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BMX General => BMX Chat => Topic started by: Mikku on September 02, 2020, 12:03 PM

Title: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 02, 2020, 12:03 PM
I know "steel is real" and we all cut our teeth on hi-ten steel or 4130 but sometimes you just have see how the other half lives. I already race an aluminium Crupi frame with carbon Answer forks but recently an unexpected opportunity arose to take a bigger step into unchartered territory and pick up a carbon race frame. Not just any carbon frame, but one of those opinion-dividing frames that occasionally causes a stir. Am snowed under with work at the moment but here's a sneak peak of what I drove home with yesterday!! More pics and story to follow at the weekend, if not before. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 03, 2020, 02:44 PM
Pumped up the tyres and took it for a maiden spin around the rice fields this evening! :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 03, 2020, 11:17 PM
So here are some more pics of my new toy! It's an interesting bike for sure. Based on a 2010 frame, the third and final year of UB2 production, it has a real mixed bag of components. The padded seat and assorted accessories (cyclocomputer, drink-holder, lights and lock) came off straight away but as you can see, it has some decent race parts, some road (Rotor 3DF) cranks and some mtb parts (by Canadian company Chromag and PRO bikegear)! Judging by the marks on everything, the bike has been well-used, presumably on the race track, at least in the early years of its life. It then passed hands and out of the race scene, last being used by the wife of the owner a recycle business, who decided to sell it after realising that she didn't like cruising around on it. Which is where I stepped in. :daumenhoch:

Apart from the rarity of the frame, what also attracted me were the race parts, including Renthal bars, Elevn forks and stem, and some well-worn but still straight Sun Envy rims which are laced to some Profile Elite hubs. The front spins forever and the back still has that distinctive sound from the cassette. I dare say that the latter could do with an overhaul but I'll leave that for another day. In the meantime, I'm going to break the bike down, clean it all up then take it from there. The Chromag bashguard will be coming off. The Izumi chain may be salvageable but I'll see after I've taken it off and cleaned it. Those non-stock (Smith and Mitas) frame decals on the non-drive side have got to go, though I'm hoping that the finish underneath won't have faded or otherwise be damaged by me removing them. Talking of Mitas, I had never heard of the brand until I investigated the tyres some more. Originally made by Czech company Rubena, the Speedo LTs are race-specific tyres with the LT standing for Czech Elite rider Lucas Tamme, who supposedly had a hand in developing them. In 2015/16 Rubena were then rebranded as Mitas, which explains the sticker.

After the clean up, the plan is to take the bike to the track and see how it goes. I can already feel how nimble it is just hooning around the rice fields but obviously the track is a different matter. If it's too short and/or stiff for my liking, then I may have to move it on but if not, I can start to think about what parts to use and what to swap out. The mtb parts can stay on there for the moment but I'm really not sure about that Rotor crankset! Since the chainring is a 43T, and therefore too small for me anyway, if I decide to keep the bike then I'll probably change the whole set-up to something more appropriate. On the plus side, it's certainly something you don't see everyday on a bmx, which I guess is in keeping with the frame! :coolsmiley:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Picklez on September 04, 2020, 12:05 AM
Wow, way out of my knowledge base and wacky as heck, only part I remotely recognised was the Renthals  :LolLolLolLol:.  Will follow your updates with interest though Mick, especially keen to hear your feedback on how it handles on the track, re flex/rigidity etc.  :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: HUTCHMAN on September 04, 2020, 05:19 PM
Welcome to the UB club buddy  fistblump  good score  :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 04, 2020, 10:20 PM
Thanks guys! The Renthal bars were one of the things that helped seal the deal - I've always wanted a set so if I decide that the frame's not for me, I'll keep 'em! :daumenhoch:

The alloy mtb post that's on there is 400mm, which is fine for the rice fields but not the track. I was thinking of cutting it down but need the longer post for riding, so last night I snagged a cut down carbon post online for under a tenner! Let the build begin!! Actually, if that's the case, should this thread be moved over to Tech & Resto??
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 09, 2020, 12:49 AM
A few updates. The cut-down carbon post arrived and it's perfect! Pics below of the post compared to the original and then installed. The bike looks much more purposeful with the sleeker lines. You can see from the bike pic that I also successfully removed those decals. The Mitas one peeled off easily and will live to fight another day on the back of a sticker-bombed race plate. The Smith one needed more encouragement and left quite a bit of sticky residue but I think I got most of it off with a bit of elbow grease. :daumenhoch:

Next job was the Izumi chain. That came off and had a degrease and clean, which has improved things a little but there's quite a bit of slap/noise on the (Profile Elite) chainring, so I guess it's a 1/8" rather than a 3/32" sizing. The plan is therefore to see how it rides on track. If I like it and decide to race it then I'll replace the chain with something better. If not, then I may as well save a few pennies and leave the Izumi on there for the time being, though I don't want to damage that expensive chainring so will probably swap it out at some point.

When the chain was off I had a closer look at the crankset. Made by Spanish company Rotor, the crank "is produced via a combination of forging and CNC machining and uses ROTOR's Trinity Drilling System, giving the crank an extremely high torsional resistance" according the review I found online. It has a 30mm UBB (universal bottom bracket) axle, as per the pic below. I can't show you mine because I don't have the tool to remove the bugger! That doesn't worry me too much though because with the chain removed, the cranks span smoothly and quietly through the BSA30 bearings, also by Rotor. I'm therefore inclined to leave it alone and instead focus my attentions on the Chromag bashguard. As funky as it looks, it's coming off as soon as I can undo the bloody chainring bolts! They are 6mm hex on one side and torx on the other, a combination I've not seen before. Not sure what size torx but I'm guessing T30 as it's bigger than the T25 that I have on my (not so) handy multi-tool! I reckon I'll have to replace the chainring bolts to something shorter, but will see when I get the buggers off. So that's where I am at the moment. More to follow as and when I buy some torx wrenches. ::)
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Taipan on September 09, 2020, 12:16 PM
Looks a mad bit of kit that!  ??? Interested to know the ins and out's of that one  :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 10, 2020, 04:13 AM
As mad as a "high modulus monocoque", according to the GT sales blurb. Definitely an eye-opener on several levels. Am doing some research on these as we speak, so will post up what I find down the line. :daumenhoch:

In the meantime, I got the bugger off! The bashguard that is. Bought a torx multi-tool and the T30 did indeed do the trick, finally revealing the nickel-plated Profile Elite chainring underneath. As anticipated, the hex/torx bolts were too long with the bashguard removed, but I had just enough bolts in my spares box to keep me up and running, at least until I get a matching set of new ones. Pics of the now naked-looking chainring below, together with the bashguard, which weighs about 100g so that's a bit more weight shaved off the bike. Tbh, I quite liked the red on there but I'm sure I'll get used to the new look. The black chain doesn't help, so maybe a silver replacement will be on the cards sooner than I was thinking! If that doesn't do the trick then I have a red Rennen chainring going spare, though that's also 43T and needs threaded bolts, so may be I'll just leave things as they are for the time being. That said, I also have the 44T Renthal chainring that's currently residing on the Quamen (pictured below), so I could swap the set-ups over. Actually, that's not a bad idea as the Profile chainring and black chain would look ok on the Quamen, and the Renthal ring and silver chain would like fine on the GT, plus I'll have better gearing to boot, as well as save the cost of a new chain. Hmmm. >:D

Anyway, the next step is to take this baby to the track, possibly this coming Sunday, if the weather improves!! :D
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 24, 2020, 01:56 PM
I made it to the track on Tuesday albeit only for an hour in damp conditions, so couldn't give the UB2 (or its rider) much of  a workout. However, it was good to finally get to ride the bike on a track and first impressions were positive. Unlike the Quamen, it didn't feel too small and I liked the way it handled, though it may well be a different matter on a dry and/or harder surface than the damp dirt I was on. One negative was the sloppy/slappy noise from the drivetrain, caused by that wide and admittedly slightly loose chain. The sound is accentuated on this frame, with its hollow, monocoque design, so much so that it sounds like something is rattling around inside. I therefore plan to swap over the chainring and chain from the Quamen sooner rather than later in the hope that that will tighten things up (and quieten things down), then head back to the track on a dry day to get a better idea of what it's like. That could happen as soon as Sunday, but we'll see.
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on September 28, 2020, 11:43 PM
Made it back out on Sunday, this time at a different but more importantly, a drier track! I was therefore able to get a decent amount of time on the UB2 and I can now confirm that I flippin' love it! It's not perfect and I'm still to get used to the plasticky feel and sound of the frame but man, I love how it rides. Although it has a shorter tt than the Crupi (21" compared to 21.5"), the geo makes it feel just as roomy. I definitely need to change that chain though, so that's the next step, along with some tinkering with the inner cable routing, which I realised was the cause of that annoying rattle referred to above. I'm also tempted to swap out the chromoly Elevn forks for the carbon Daggers on my Crupi? >:D

In the meantime I've picked up some replacement grips, the blue of which seems to be fairly good match for the frame. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: fattaffracingco on September 29, 2020, 06:03 PM
Loving this thread , keep it coming
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on October 14, 2020, 01:18 PM
Thanks man! Have been snowed under with work recently, so not much progress other than swapping out the grips and doing a temporary fix of the cable rattle!
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: bobafett on October 14, 2020, 04:09 PM

Looks mad and reading the thread it sounds mad too  :shocked: :LolLolLolLol:

Have fun with her  :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on October 17, 2020, 12:02 AM
Yeah, it is a bit different I know! Actually took it out for a spin around the rice fields yesterday and it feels so much more lively than the Quamen (my now-usual rice field rider)! Still can't get used to the sound of the frame but it feels great to ride! I really need to crack on and swap out the chainring and chain then take it back to the track! :D
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: bobafett on October 19, 2020, 10:24 PM

Still can't get used to the sound of the frame


I kinda want you to do a reverse of the old cardboard on the frame hitting the spokes trick from back in the day..... but this time with the card  taped to the spokes and it smacking the frame to see if the sound resonates through the body and sounds like your on a motorbike  :2funny:

I'll get me coat...... :-[ :LolLolLolLol:

Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on October 30, 2020, 11:27 AM
I kinda want you to do a reverse of the old cardboard on the frame hitting the spokes trick from back in the day..... but this time with the card  taped to the spokes and it smacking the frame to see if the sound resonates through the body and sounds like your on a motorbike

^^^ "nono" ^^^

Last Sunday I finally got round to swapping the chainrings and chains between the Quamen and GT. However, as always, things didn't quite go according to plan. Removing the Renthal chainring and KMC chain from the Quamen wasn't a problem, since I'd fitted them in the first place. The first hurdle I encountered was getting the bloody pedal off the UB2. Whoever had worked on the bike before had tightened the allen bolt up so much that I began to question whether I was trying to turn it the wrong way. After copious amounts of swearing and WD-40, it finally undid, leaving me with a bruised hand for my efforts. The Renthal chainring went on and looks great. I then went to fit the KMC chain and found it was too short, which I had feared would be the case since I no longer have the spare links for that chain. Even moving the wheel all the way back in the drops wouldn't have been enough, not that I want to alter the wheelbase as I like how it currently rides. So, that has forced me to doing what I really should have done to begin with (but was being tight-fisted), namely to buy a new chain for the UB2. That led me to my next problem - what chain to get? There are plenty of 3/32" options online but less of a choice from Japanese sellers. However, a bit of searching led me to a KMC Z610 HX, which I was able to snag for a not unreasonable 9 quid shipped to my door. That should arrive next week, so more updates and pictures then. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 08, 2020, 12:22 PM
The KMC chain arrived this week and as anticipated, needed a few links taking out. I went to loosen the back wheel and found that the same gorilla who had cranked on the pedals, had applied the same amount of force to the axle bolts! Admittedly my 8mm allen key is only a multi-tool one but there was no budging the bugger! I therefore sprayed both bolts with WD-40, left them overnight then the next morning, went to my local home centre to buy a longer allen key. Thankfully the combination of the two worked and the wheel was soon free, so I could measure up and break the chain to size. The UB2 has its own chain adjusters and one of the bolts is missing from the non-driveside - not a big deal but I'll try to see if I can find one as and when. A bit of adjustment with the remaining 3 bolts had the chain tensioned and following a bit of fiddling with the brake pads, it was time for a test ride. I could immediately notice how much smoother not to mention quieter the drivetrain was, so all's well that ends well. Plus I much prefer the look of the Renthal ring to the Profile one it replaced. The next step is to sort out the cable rattle, which I couldn't do because I've run out of cable ends, so that will have to wait until I pick up some more. In the meantime, here are some pics of the new set-up including the chain adjuster. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 09, 2020, 08:50 AM
So today I had a quick dig around my non-race spares box to see if there were any brake cable ends and although I drew a blank, I did find some other goodies. I've been looking to buy a padset and number plate for the UB2, as I definitely intend to race it at least once, and don't need much of an excuse to get a number plate fix! I have already seen some potential purchases online but the cost of shipping to Japan often makes things prohibitive unless I can combine purchases and postage. Anyway, rummaging though the box I found a NOS Boston plate and some black pads - perfect! & free!! Well, not really, as I did buy them at some point but I'd forgotten about them plus now I don't have to buy other stuff, so they kind of feel free! :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: HUTCHMAN on November 09, 2020, 11:33 AM
Nice one... good find on the pads n plate.......  a proper pad for the frame may be an issue so i guess it's an old duvet and shed loads of gaffa tape  ;D
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 09, 2020, 10:46 PM
Yeah, the top tube design doesn't really lend itself to pads! Below you can see the pads that came with the original frame kits. The top tube pad basically sticks to the top of the top tube, a look which I'm not a particularly big fan of. Thumbs down Thankfully I only run bar and stem pads on my race bike, mainly to stop the plate rattling but also as a little nod to the old school. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 14, 2020, 11:08 AM
Picked up some cable ends today, so was able to remove the old one and slide on some plastic tubing over the cable which will hopefully fix or at least reduce the cable rattle. Will find out tomorrow when I head back to the track to give the new chainring set-up a whirl. Here are few pics from this afternoon's shakedown ride. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 16, 2020, 10:32 PM
Sunday's track test was a big success, with the bike now feeling and sounding a lot better. I was soon confident enough to give it the same amount of stick as the Crupi, so that was good. Autumnal pic attached! 8)

Next step is to swap over the carbon Daggers from the Crupi. Weight-saving aside, in the same way the chainrings look better on their new rides (the Renthal on the GT and the Profile on the Quamen), I think the forks will look better swapped over too. These Elevn forks look too small and slim for the UB2 frame, whereas will probably look fine on the more conventionally styled Crupi. Likewise the chunkier, bladed Daggers will balance up that slab of carbon on the GT! I think! We have a 3-day weekend coming up, so hopefully I can work on the bikes on Sunday and if successful (famous last words), take the GT for another track test on the Monday. Maybe! :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: OrgasmDonor on November 17, 2020, 03:51 PM
love querky me, thats cool  :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 21, 2020, 12:14 PM
Querky's good! :daumenhoch:

Fork update. After playing around with crown races and headset spacers, the UB2 is now wearing the Answer Daggers from the Crupi, with the Elevn forks having moved the opposite way. As anticipated, the chunkier carbon forks fit the frame much better than the slimmer Elevns, at least to my eye. Moreover, the switch of forks has shaved a bit more off the already light weight of the complete bike. According to my scales the Daggers came in at 620g, 220g less than the (840g) Elevns. The difference was certainly noticeable when holding them, so it will be interesting to see how that translates on the track. Below are a couple of pics of the forks in their new homes.
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 21, 2020, 12:28 PM
Here's a couple of before and after pics. I only had time for a quick test ride today, so tomorrow I'm going to check that everything's snugged up nicely, then switch over the magnesium DMR V12 pedals, also from the Crupi. If all goes to plan, I'll then head back to the track for a proper test. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 24, 2020, 01:59 AM
What better way to spend a national holiday than to hit the track! Sunny weather yesterday meant I was able to test out the UB2 with the Answer forks - an all carbon set-up! Unsurprisingly, the front end felt lighter and it was noticeably easier to lift up - not that it was difficult before but it just pops up easier now, as per the pic below. I need to borrow my neighbour's scales again because with the addition of the Daggers and magnesium DMR V12 pedals, also from the Crupi, the bike should now be around the 18lbs mark. :daumenhoch:

Save for a bit of tinkering here and there, and possibly a change of tyres, I'll about done with making any more major changes. New cranks would be nice but are an unnecessary expense at the moment. I'd prefer to spend my hard-earned on an overhaul kit for the Elite cassette, which sounds okay to my untrained ear but I'm assuming they're the original pawls and springs in which case they must be quite a few years old by now. So that may be a Christmas present to myself or I may just save that for next year's race budget! ;D
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on November 28, 2020, 11:01 PM
I borrowed my neighbour's bathroom scales again yesterday and with the Answer forks and DMR pedals, the GT's now coming in around the 8.2kg mark, which is about 18.08lbs in old money. I say "around"  and "about" because the readout moved slightly if I moved, so it's all approximate. Still fairly pleased with that though, especially seeing as I wasn't thinking much about weight-saving when I picked this up and started playing around with parts. :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on December 05, 2020, 10:15 AM
Just a small update today. I tried and failed to find a replacement chain-tensioner bolt (to replace the one that had gone AWOL) but apparently a 40mm, M4, fully-threaded, allen head bolt is not a commonly-used item in Japan! I therefore resorted to our Chinese friends on eBay and ?1.25 and 10 days later, 5 shiny new bolts arrived. I had my doubts they would a) arrive and/or b) fit, but thankfully they did and do! :daumenhoch:
Title: Re: Tempted to the dark side - GT Ultrabox 2!
Post by: Mikku on December 06, 2020, 10:50 AM
I have just managed to pick up some of my favourite race tyres, the Maxxis DTH, which are getting harder to find since Maxxis brought out the Torch. Like the UB2, the DTH was designed for the Beijing Olympics and although tyre technology has moved on, so has carbon frame design, so I think the two are well-matched. :daumenhoch:

The Rubena Speedo LTs that were on the bike are actually slightly lighter than the 345g DTH. There were two versions of the Speedo LT, an economy version weighing 580g and an Elite version made from a "carbon racing extreme light tread compound". The ones on the GT weigh about 330g, which is the quoted weight for the Elites. I quite like them but since most of the tracks I run at are dirt, some still with dirt berms, I prefer the extra tread of the DTH. Plus they have a slighter lower profile than the Speedos, which I think gives the bike an even sleeker look. 8)

When swapping over the tyres I had a look at the tubes and these are made by Onza, yet another new-to-me brand. They looked in good nick but are a 1.75-2.20" size, so I'll keep them for the time being but may replace them with a newer, smaller pair down the line. So that's about as far as I want/need to change things for the moment. I could do with another track test but that may now have to wait for the New Year. In the meantime, I think I've done enough to this bike to justify entering it in BOTM! :D
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