# "Grown Up" BMX project



## ChrisEyles (3 Feb 2019)

I've been gradually building up my MTB skills over the last few years and while I've made a lot of progress, I've always struggled to get the hang of manuals and jumping. 

So last summer I got myself a BMX to learn some skills, on the basis that there's a pretty good BMX race track and park where I live. This actually worked pretty well - I can now manual a bit, do a small but "proper" front-wheel-first bunny hop and am a lot more comfortable getting a bit more air on jumps. 

However, being a BMX it was not at all comfortable or versatile, and I felt like a complete tit riding it. 

I want to keep my current MTB as it is, which is set up with low bars and a medium reach - brilliant for XC riding on bridleways with road links but rubbish for learning/improving these skills. 

So I'm planning on selling the BMX and building up a 26" jump bike frame to hopefully bridge the gap. I'm looking for something I can work on the mechanics of manuals/jumps, while not being limited to riding in town and hopefully not looking like too much of a plonker on! 

Plus I haven't done much tinkering over the last year and I'm itching for a project!


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## ChrisEyles (3 Feb 2019)

Aiming for something a bit like this: 










I've also been wanting for ages to strip and polish up an ally frame, so may give that a go too. 

Intended budget around the £100 mark so if it doesn't work out I can sell with no loss (knowing that I always over-run a bit!). 

There, now I've put my cards on the table I'll keep this as a build thread and see how it works out!


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## fossyant (3 Feb 2019)

A full size jump bike would be OK - should be able to do it on a budget - suspension forks or not ?

I aim to get my skills up shortly, as seeing MTB is my main riding now. We've got Dirt Factory opening up this month in Manchester (an indoor MTB park).


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## ChrisEyles (3 Feb 2019)

I've been trawling ebay/gumtree for a local jump bike for a bit now. There is a GT chucker frame going nearby which I'm very tempted by, but no complete bikes in budget.


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## ChrisEyles (3 Feb 2019)

Not too fussed either way about sus forks. I fear those within budget might explode when I inevitably case a few landings, but then again I subjected an old pair of RST forks to considerable abuse and they were fine. 

Haha, OTOH the springy rebound on a cheap pair might help pop that front wheel up


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## DCLane (3 Feb 2019)

I built a 24" wheel single speed MTB for my son out of a Spesh Hotrock - great fun and with a 400mm seatpost anyone could ride it.


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## SkipdiverJohn (4 Feb 2019)

I agree it looks somewhat ridiculous seeing a grown bloke riding a kids sized BMX, but why not just use a regular MTB converted to single speed and maybe in a slightly smaller frame size, but not silly small? Pretty much anything with a strong frame and two wheels could be converted I would have thought.


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## ChrisEyles (5 Feb 2019)

Well, I've now got a frame to build up, this GT Chucker: 





The paintwork does look a bit shoddy, so it's a good excuse to have a go at stripping & polishing the frame. I've borrowed a bench grinder with a soft buffing wheel to hopefully save some elbow grease. 

I used the proceeds from selling the old BMX to get a donor bike off ebay for parts to build the frame up with. Picked it up today and looks like it should do the trick, but haven't had a chance to give it a really good once over yet. 

So far the budget is doing all right: 

Frame - £30
Donor bike - £51.50
Paint stripper - £4

Total £85.50

I'm sure I'll find I need some other bits and bobs as I go, but will hopefully manage to claw a bit back by selling un-needed parts off the donor bike. 

Just need to find some time to do some tinkering!


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## JhnBssll (5 Feb 2019)

Looking forward to seeing your progress on this. I used to have an old Azonic DS-1 built up as a jump bike, sold it about a decade ago but it was an ace bike - this one looks like it could be a lot of fun too  Nitromors paint stripper has always done the job for me, what did you get? £4 seems cheap lol


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## ChrisEyles (9 Feb 2019)

I had a go at stripping the frame today. It turned out to be a bit more faff than I'd hoped (possibly due to the cheap paint stripper), easy to slop on but messy and time consuming to remove and I'm clearly going to need to give it another go to finish it off. 











You can see it didn't take the decals off either! 

Might have another crack at it tomorrow if I get time. I reckon it'll look pretty good when it's finished though.


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## ChrisEyles (9 Feb 2019)

I split up the donor bike today too. Given that I bought it sight unseen I'm fairly pleased with it. 

The good - wheels and brakes all fine, decent tires and the fork is better than expected, even has working rebound adjustment. Headset should fit in the zero stack head tube of the GT frame with any luck.

The bad - FD is seized (wasn't going to use it but was going to sell it!), chain is stretched out, 12t sprocket has 2 missing teeth and shifting on the rear is very dodgy. Crankset is riveted together so need another one to go 1x up front.

The ugly - well the BB did give up and come out eventually!


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## ChrisEyles (10 Feb 2019)

Finished off stripping the frame today. Well, I say finished... Couldn't get all the paint out of the tricky corners and I discovered a bit of a crack in the seat tube just below the top tube, so decided "sod it" and called it good enough. 

It was never going to be a pristine build so I'm not too gutted about the crack (I'll charitably assume the guy who sold it to me didn't notice it under the paint either). Will just have to watch the seat post insertion height and keep an eye on it.

Here's a mock up showing how it looks at the moment: 









I quite like the brushed finish but will have a go with the bench polisher next weekend to see if it looks even better shined up. 

Just don't look too closely, there's blue paint lurking!


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## ChrisEyles (10 Feb 2019)

Don't think I'm stripping another frame myself though, it's a right faff!


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## JhnBssll (10 Feb 2019)

Looks great


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## tom73 (10 Feb 2019)

Looking good


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## SkipdiverJohn (11 Feb 2019)

ChrisEyles said:


> Don't think I'm stripping another frame myself though, it's a right faff!



Why did you need to fully strip it though? Couldn't you have got the decals off with a heat gun & thinners then just given the old paint a rub down? That's all I've done with hack bikes I've repainted. If I wanted a quality job I would go for shotblasting & powder coat.


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## ChrisEyles (11 Feb 2019)

That's exactly what I've done when I've repainted bikes in the past, and it always works really well.

This time I wanted to try polishing up the bare frame, hence the need to strip off all the paint.

Quite looking forward to getting the buffing wheel out next weekend.


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## ChrisEyles (15 Feb 2019)

Managed to give the frame a quick buff and polish tonight. Was a lot quicker, easier and more rewarding than stripping the paint! 










It's far from a mirror shine but I'm happy with how it turned out. Should look ok as the aluminium oxidises too. I might give it another polish before starting assembly. 

What's less good is I found another crack while polishing the frame. This one's in the top tube just under the head tube. Doesn't look horrendous, but means I'd have to get another frame if I wanted to learn to do bigger jumps. Should still hopefully do the job for manual/wheelie practice and general messing around though... Guess that's what you get for buying cheap frames off teen-agers on facebook


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## ChrisEyles (15 Feb 2019)

Going to put the headset cups in next - lacking the proper tool, is it best to use a wooden mallet or a vice and two blocks of wood? 

I've done the former in the past with no problems, but that was on a steel frame with external cups.


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## ChrisEyles (17 Feb 2019)

Gave the frame another polish today and finished it off with a rub down with some GT85. It looks good, I'm really pleased with it. Will be interesting to see how quickly it dulls as the aluminium oxidises. 

Sold the old crankset and bought a new one - puts the total net spend so far up to £88... and I think I now have everything I need to build it up (granted quite a few bits are coming out of the parts bin so arguably cheating a bit on the sub-£100 build but never mind, they are just going to sit in the garage otherwise). 

Had another close inspection of the frame and can't decide whether the marks on the seat and top tube are cracks or surface scratches. Either way they will need keeping an eye on when it's built up to ride.


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## tom73 (17 Feb 2019)

Great work on the frame going to look great when you’ve finished


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## ChrisEyles (21 Feb 2019)

Managed to get the bike mostly built up yesterday evening. 

I went with the wooden mallet method to install the headset races in the end - worked fine with no drama. 

Re-used the old BB from the donor bike and gave it a bit of a clean and squirt of oil. It still feels a bit rough but should be serviceable enough. 

Seat post & saddle, wheels, brakes/levers, grips, rear shifter and mech & all cables came off the donor bike and all seems good there. I also swapped out the broken 12t sprocket on the cassette for a 13t one and re-jiggled the sprockets with some from the parts bin to give more sensible ratios (I don't know if what was on there was original but it seemed oddly specced to me). 

Bars & stem came out of the parts bin. I do have a set of GT bars/stem which look the business, but they have quite a bit more reach and less rise so I've used the ones pictured instead to give it a more playful feel with a short, high front end. I've got an old chain and chain ring set aside for the build too. 

Just need to wait for the ebay'd cranks to arrive and I can finish the build. Pretty pleased with how it's looking now though. 












Shifting was awful on the donor bike, and I'm not sure why, so keeping my fingers crossed the new chain and different sprockets might fix that. Also need to cut the seat post down a little so the seat can be properly slammed for practicing manuals. 

Budget is going better than expected: 

Frame £30
Donor bike £52
Crankset £12

Sold front shifter -£3
Sold old crankset -£10
Sold old handlebars & stem -£5

= Total net spend so far of £74


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## tom73 (21 Feb 2019)

Nice one


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## ChrisEyles (2 Mar 2019)

Crankset arrived in the post this week so I've got all the bits I need to finish it off. 

Just setting up the indexing on the rear mech and truing up the wheels before I take it for a spin.


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## roadrash (2 Mar 2019)

enjoy


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## tom73 (2 Mar 2019)




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## ChrisEyles (2 Mar 2019)

Just got back from a quick spin around the local BMX track. 

Everything's working nicely and the shifting now seems OK with a newer chain. The forks are a bit clunky but actually feel alright besides the noise they make. 

With the seat down it feels a lot like a less twitchy BMX - which is great, just what I was aiming for. At the moment I am looping out the back a lot when trying to manual/wheelie, but if I ever get time to put in some proper practice it should be pretty good for that. 

Will try it out on a local bridleway route when I get the chance to see how it feels on that, I reckon it could be quite good fun.


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## ChrisEyles (10 Mar 2019)

Couple of tweaks today - put on a 100mm stem and slightly narrower bars just to see what it would feel like. Getting to the manual balance point requires a slightly more forceful movement, but it seems easier to hold it there. Feels better jumping on the BMX track too. 

Quite surprised as I'd have thought a shorter stem would have been better on both counts. 






Tipped the seat angle back too, which made a big difference to ease of wheelies. It's not quite as drastic as the pic below now though. 






I always assumed that my inability to manual/wheelie was solely down to lack of skills, but it seems bike set up is pretty important too.


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