Strange rub/wear spot on seat stay AC 29er

[Joeydutch]

Hi guys,

Has been a while since I posted. Was enjoying my AC 29er the last couple of years ;-)

I think my AC 29er was one of the custom 29ers after Whafe got his, anyway before Nicolai took it in his regular portfolio.

I am very happy with the bike although I have a couple of things which got me thinking about a replacement (AC 650B Pinion :-).....

First I would like to have a bit more suspension on the bike. I am currenty running 100 up front. people are howveer telling me that the frame would allow up to a max of 120. You guys agree?

One other thing is that I have a strange 'rub' spot on the seatstay. See the pic. You can actually feel that the alu has come of. The seatstay is a bit flat on that spot. Anyone an idea whether this is 'normal'?

[norcosam]

The tyre is touching the frame under full travel.

[Joeydutch]

Thx

Though about that. However, should have noticed it (sound etc) and I think that tyre rub would not couse the alu to grind of.

I personally think its sand/dirt grinding it of. Should' t be normal should it? If its that sand other should have the same problem.

[norcosam]

One way to see if its the tyre is to remove all air from rear shock,gently sit on it until it fully compresses and check to see if the tyre is touching.
If you have a coil rear,remove spring and do the same as above.

[Joeydutch]

OK, good tip. I'll check. But do you think that - provided all specs are followed - the tyre should be able to touch? In other words, you think it is a geo fault if it touches?

[norcosam]

Its difficult with tyres,They all seem to vary so much in size.I have a 2.25 nobby nic and a 2.35 Hans Dampf,shouldnt be much in them size wise,Yet the Dampf is a massive tyre compared to the Nobby Nic.
It could be a build fault,but could be that the tyres your using are bigger than they allowed for.
Noticed on another thread that Hans Dampf dont fit some frames,Yet i run one in my AC 26".Fits no problem.

[Joeydutch]

yeah. I usually run the Dampf up front and RR or NN at the back. Ran Geax Saguaro for a long time on this bike. Not a real massive tyre.

I'll check with Nicolai about this. I saw they changed the geo a bit in the final 29ers compared to my custom geo.

[norcosam]

Ran Hans Dampf front and rear for a while,Awesome grip,excellent tyre.Was a bit of a slog sometimes on climbs.
Now its muddy and wet,probably wouldnt notice

[The_Lecht_Rocks]

nbby nic 2.25" on my ac29er at the bak - zero rub under full compression fwiw.

[Boozzz]

Have the same on my FR with a 2.7 Highroller at the back It's definitely the tyre rubbing a hole in your frame.

[Joeydutch]

Still think it's a strange issue. Feels like I'll be through the alu in abother year of riding. Should also have an effect on the strength of seatstay I assume.

Protectiion won't help if its the tyre rubbing. It'll rub straight of. I a chainstay sticker protector (from my racer) but that dind't even last one ride

[dipper]

Joey has your frame got the new 8mm alu front shock mount(as per all other helius models) or the welded on 6mm mount?

[Joeydutch]

Think the welded 6 mm one (with the seperate positions holes)

[Warp]

Definitively the tyre hitting the seat tube (it's not a stay, it's the seat tube itself)...

Geax tyres are not wide, but they tend to be tall, I had a Sturdy which is not close to the 2.25" claimed, but it's taller than many 2.4s

I can't speak for Hans Dampf, though.

Move your shock one hole down in the rockers in the meantime. According to the chart, you'll run 108mm of travel instead of 120mm but this will keep the tyre from hitting the seat tube.

[dipper]

Think the welded 6 mm one (with the seperate positions holes)

thats what i suspected. ive pm'd you

[Whafe]

Sorry for slow reply, I have not got the issue at all that you mention. Am thinking it will for sure be tyre size.. As Sam mentioned, hope you have let the air out of the shock and cycled the travel threw, will tell you straight away..

You haven't been running your shock with to little air pressure?

[Axe]

Easy fix would be to shim travel in the shock. Look for instructions in 650b forum, many people did that.

Do you run 57mm stroke instead of 50mm stroke by any chance if that is a 200mm shock length? That could do that too. In this case, definitely shim it, or get a proper shock.

Current version calls for 57mm stroke, but yours could be different.

If it is a Fox shock, in US one can send it to Push for Factory Tuning System Big Hit Kit rebuild. It includes a conical bumper that will ramp up resistance at the very end of the travel and prevent it from bottoming out harshly.

If you ride it as is, stick some helicopter tape over the spot. Touch it up first.

[Joeydutch]

@Whafe: sent you a PM

Thx everbody for the input! I am working it out with Nicolai.