Seat stay bridge rubbing tires - can I grind?- Mtbr.com
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  1. #1
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    New question here. Seat stay bridge rubbing tires - can I grind?

    I picked up a new Bianchi Sok 29er last year for a great deal. One strange thing about it though is that the tires it came speced with (WTB Exiwolf 2.3) have enough volume that at times the lugs rub the seat stay bridge where the tread meets the sidewall.

    If I am running low pressure (~30lbs) they will not touch, but anything more that that and at first just one small spot rubs with the minor variations of the tire/wheel. Then if I go up to say 50lbs, the tire rubs all the way around and is unridable. I could of course fix this by getting different tires but I do like to run big volume and it's weird that the tires that came w/ the bike don't even fit (perhaps that's part of why it was a deal!).

    Anyway, the tolerance is close enough that I think grinding 3-4mm into the bridge on the left and right sides of the tire will fix the problem. The bridge is pretty thick and I don't think it will cause structural problems however I'd like some input from the experts here? Is it worth messing with?

  2. #2
    Frame Building Moderator
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    Grind it.

    With the caveat that you will obviously void any warranties, I would go ahead and do it. The seatstay bridge is not very important, structurally (you can even completely remove it and the bike will not ride all that much differently). So I say go for it, assuming you want to keep using your current tires.

    -Walt

    Quote Originally Posted by punkrocknj View Post
    I picked up a new Bianchi Sok 29er last year for a great deal. One strange thing about it though is that the tires it came speced with (WTB Exiwolf 2.3) have enough volume that at times the lugs rub the seat stay bridge where the tread meets the sidewall.

    If I am running low pressure (~30lbs) they will not touch, but anything more that that and at first just one small spot rubs with the minor variations of the tire/wheel. Then if I go up to say 50lbs, the tire rubs all the way around and is unridable. I could of course fix this by getting different tires but I do like to run big volume and it's weird that the tires that came w/ the bike don't even fit (perhaps that's part of why it was a deal!).

    Anyway, the tolerance is close enough that I think grinding 3-4mm into the bridge on the left and right sides of the tire will fix the problem. The bridge is pretty thick and I don't think it will cause structural problems however I'd like some input from the experts here? Is it worth messing with?

  3. #3
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    Walt - Thanks for the input, I have heard that Bianchi is a bear to deal with re: warranty issues anyway so if I run into a problem down the line... hey time for a custom frame

  4. #4
    Frame Building Moderator
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    Afaik...

    ...Bianchi no longer makes any mountain bikes. So yes, I would assume that getting them to warranty anything is a PITA. Modify that sucker, ride it into the ground, and have fun!

    -Walt

    Quote Originally Posted by punkrocknj View Post
    Walt - Thanks for the input, I have heard that Bianchi is a bear to deal with re: warranty issues anyway so if I run into a problem down the line... hey time for a custom frame

  5. #5
    Squelch the weasel.
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    Quote Originally Posted by punkrocknj View Post
    ... the lugs rub the seat stay bridge where the tread meets the sidewall.

    ...

    I think grinding 3-4mm into the bridge on the left and right sides of the tire will fix the problem.

    Hey, just to be clear, you are saying that the tire rubs the seat stay bridge, or the seat stay? Because I'm not clear how the tire can rub the bridge "where the tread meets the sidewall", or how you can grind at the bridge on the left and right sides of the tire.

    Don't grind away the seat stays. While this is more punk than grinding at the seat stay bridge, it might cause your bike to not last as long.

  6. #6
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    Thats what I thought. But I found a pic of the SOK and it has an inverted V plate for the bridge. I can see how that can rub the sides of a tire.
    Attached Images Attached Images  

  7. #7
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    Thanks for the potential heads up Jaques - but smdubovsky's photo is correct. The edges of that inverted V clip the lugs. I can see how it wouldn't be that way with most bridge designs but it's the bridge itself that hits on the Sok. Even on that photo it looks like they are rubbing!

  8. #8
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    OK! Sorry for the unneeded alarm then. The Sok I've seen had a more standard bridge.



    (This is not one I've seen - just grabbed that image off the 'net.)

    Happy grinding!

  9. #9
    Relax. I'm a pro.
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    What a shitty design.
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