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Recently my commuter bike (cannondale quick 5) was stolen, so I decided to get an old road bike off of craigslist - a '91 specialized sirrus triple. The guy I bought it from had bought it new, used it for about a decade, then hung it up in his garage until this past month. I took it in to REI for a tune-up and some new tires and asked if they could put on tires with a bit more traction, knowing that I'm accustomed to my commuter bike and probably wouldn't do too well with slick tires.

When they put on the new tires (I'm not talking knobby mountain bike, just a little bit of tread - Michelin City tires) they had me sign off that the change in tire size meant the rear wheel would have to not be completely in the dropout - currently it's about halfway in the dropouts and has scant 1/8" clearance from the rear brake assembly; if it was all the way in the dropout it would have no clearance whatsoever.

Is this (the rear wheel not being completely in the dropout) ridiculously unsafe? I've never had to deal with this before, but it seems like this would be ridiculously unsafe.

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do you know (a) what size tyres the bike had originally and (b) what size tyres are on now? – PeteH Jul 27 '13 at 16:12
What kind of dropouts does the bike have? Semi horizontal, vertical, track? – Benzo Jul 27 '13 at 16:17
This is not wise. Not only is the wheel apt to come loose, but also the derailer will not properly mesh with the rear cluster. But from the looks of it (a few pictures on Google) that bike is a pure road bike with very little tire clearance -- very likely any tire larger than 25 or so is going to be too large. – Daniel R Hicks Jul 28 '13 at 2:45
If your wheel becomes even a little bit loose, it seems to me that your wheel would then seize up causing you to unexpectedly come to a possibly very dangerous and/or catastrophic stop – Joe Jul 29 '13 at 14:47
What makes you think that slick tires have less traction than treaded ones? On asphalt at least that's not the case, even in heavy rain, because the very small width (you have on a road bike) makes swimming up on the water impossible. – arne Aug 13 '13 at 16:26

Yes, it is unsafe. You should find a set of tires that will allow you to seat the wheel properly into the drop out.

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And most city tyres go down to a 23 or 25 anyway. As @arne says, aquaplaning is impossible, so that's fine - but if your route is anything like mine (muddy/dusty patches on top of tarmac cycle paths/roads) a little tread may help. – Chris H Sep 2 '13 at 9:37

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