[Closed] Carbon fork users - A little help please 🙂

Looks like a Pace RC31 to me? I can check when I get home, although no doubt someone else can beat me to it.

What size of fat tyres are you trying to fit in? I've got 2.3in in with loads of room to spare.

I know there's not enough clearance for a fat bike tyre (tried it). My On-One carbon fork is about 87mm.

Maybe if you used a narrow rim the fat tyre would be narrower, eg:
On a 40mm a Larry = 88mm
On a 80mm a Larry = 98mm

PS - I know 2.3in isn't fat! Will get the measuring tape out tonight to see if these size up marginally bigger than the On-Ones. I don't think you'll get a proper "fat" tyre in though.

Cheers epicyclo.

Having a 48mm VIZ rim built up at the moment into a 100mm FH to play about with a 3.0 Galzoldi (sic) in my Salsa forks (90mm clearance.

I am getting the feeling that this FAT stuff is addictive and so was wondering if I could get a pair of 100mm spaced front forks that would take a proper fatty 😳

I am guessing that a larry on a 48mm rim would be too wide for my forks 😕

That's why I bodged up my own fork when I wanted to try it. 🙂

Just need an old suspension fork + a bit of butchery = homemade rigid fork that takes a fat tyre to 88mm.

epicyclo - Member

That's why I bodged up my own fork when I wanted to try it.

Just need an old suspension fork + a bit of butchery = homemade rigid fork that takes a fat tyre to 88mm.

Hmmm.

My Salsa forks have a clearance of 90mm 😕

I am guessing that a larry on a 48mm rim would be wider than 90mmm

Ho hum.

Back to the drawing board 🙁

It wouldn't hurt to buy a tyre and tube to try it on your wheel. Not every tyre is exactly the same and if you run low pressures you may have a smaller cross-section. I think mine were measured at around 10psi whereas it seems the best pressure is around 5-8psi.

You're going to need the tyre and tube sometime anyway.

I measured our Pace RC29s last night - 93.5mm clearance parallel top to bottom. Would be interested to know how you get on.

epicyclo

Re. your fork bodge...you are using different uppers yes? Are they clamped in at the bushings?

Just wondering if/how to do this using 1 pair of forks.

Different uppers, yes.

The lowers are steel from a cheap set of forks. Only used them because I wanted to clamp them so I could adjust the height if necessary, and I prefer steel for this job.

However if you don't want the adjustment - it isn't necessary if you know the A-C you want - then you may be able to use the lowers that came with the fork. Without seeing the internals of your fork or knowing what the lowers are made from it's difficult to give advice.

What I was going to do if I used alloy lowers was to bond them, and I may be doing this shortly as I'm trying to work out a bodge for a 135 spaced front fork.

I would expect to find the lowers slightly loose on the stanchions because at the bottom end of the lowers the stanchions are past the bearing surfaces. Procedure I am intending to use:
1. A thorough clean to remove all traces of oil.
2. Make up height spacers (if necessary) to stop the stanchions going in too far. I'd probably use something light like a section of thick broom handle - that would be glued in. It would be topped with a large steel washer for the stanchions to bear on. (This is a fail-safe and not necessary if the bonding of the stanchion to the lowers is done properly)
3. Assemble the fork loosely with the stanchions lying on blocks and the lowers bolted in to an old axle which is also blocked up to keep it in alignment. Looks ok? Then,
4. Clean the inside of the lowers and the outside of the stanchions again.
5. Mask off the bits you don't want glue on or you'll be sorry 🙂
6. Using a suitable grade of epoxy* slather the inside of the lowers and the outside of the stanchions with it and assemble the forks making sure they are properly lined up. Epoxy is a gap filling glue so you can have some latitude in your gaps.
7. Trim off excess epoxy when it sets to a hard cheese state, but be careful not to knock the alignment.
8. Allow to cure.
9. Once it's done if you're nervous about the joint failing, drill a hole right through and put in a pin or such like.

As I said that's how I'd go about it, but I can't guarantee it would work, and there is always an element of risk with this sort of thing.

The more of the lower you use, the larger the bonding surface and the stronger the joint will be.

If you look at the bottom of most carbon forks and alloy forks that are constructed the same way, you'll see that they only need a few inches to get a good bond. For my amateur attempts, I would go about least 50% more.

*I'll probably mix up my own mixture, but basically it will be a good quality epoxy with aluminium powder.

BTW if you're on good terms with your lbs, they usually chuck out a few sets of once premium forks each week. A suitable donation of cake and biccies may earn you the right to scavenge in their bins 🙂

Edit: I'm waiting for some alloy to make a fork crown, and once that arrives, I'll probably be building the fork. In which case I'll post up the whole procedure. However Xmas and the StrathPuffer may get in the way.

Thanks - am on great terms with lbs as I used to work there - don't recall many suss forks getting chucked though!

would expect to find the lowers slightly loose on the stanchions because at the bottom end of the lowers the stanchions are past the bearing surfaces.

*confused* are you talking about removing the bushings?

Am also concerned re. bolting through magnesium lowers...but otherwise that's how I'd do it too.

cynic-al - Member
...don't recall many suss forks getting chucked though!

Your locals are obviously a bunch of mincers then...
(or maybe they look after their bikes better) 🙂

...are you talking about removing the bushings?

I would remove the bushings purely because I don't know how they are fastened. If they were metal and easily re-used, I would consider using them as a shim to fill the gap.

Am also concerned re. bolting through magnesium lowers...

I won't be doing this myself - it's just another failsafe, and I'm confident the epoxy bonding will work.

IIRC the snow-bike guy asked for mashed forks recently but I can't find the thread 🙁

May ask at lbs.

One trip (and £0) to another lbs (former colleague works there) later...

[url= http://farm6.static.flickr.com/5283/5260911460_5656278ee5.jp g" target="_blank">http://farm6.static.flickr.com/5283/5260911460_5656278ee5.jp g"/> [/img][/url]
[url= http://www.flickr.com/photos/7693620@N05/5260911460/ ]IMAG0188[/url] by [url= http://www.flickr.com/people/7693620@N05/ ]alan cole[/url], on Flickr

Hope you provided cake and biccies...

Looks like plenty of travel on them so the stanchions are probably long enough that you won't need spacers at the bottom. Plenty pics of the process, please.

Biccies will have to be delivered on return trip...

I was thinking that might be a benefit too but the more I think about it the more I am wondering about how to get glue/filler in beneath the bushing.

Just be careful - the bushing may be teflon (or similar) coated and so may not be a good base.

Best to dismantle the forks and see what's in there.

Indeed. Wondering how to get it all true without them though.

Probs a project for the Xmas hols...

Actually I was thinking about a suitable matrix to replace the bushes for my next job.

Possibly a very thin piece of Carbon Fibre cloth. Wet down with epoxy, tight wrap around stanchion, allow to cure to cheese state, trim to fit in lower, then slather in epoxy, insert, and block up for alignment. Allow to cure.

I haven't yet decided whether to do it that way or to simply use thickeners on a single operation.

(I'm not thinking the c/f will make it stronger, but it may make alignment easier)