treebound 

I’ve got a 2008 Trek Equinox E7 that will not fit new tires larger than 20mm. It was originally spec’d with 700x23c tires, but modern 23c tires are apparently taller than older 23c tires. I tried putting some new 700x23c tires onto the bike but the rear one contacts the seattube hard, and with the vertical rear dropouts there is no way to move the wheel rearward. I managed to find some Continental 4000 700x20c tires that do have clearance enough to run them on the bike.

Lately I’ve been thinking about machining the rear dropouts to allow the wheel to move rearward enough to run 23c tires. Functionally I think there is enough room to do this which would leave the rear dropouts with an L slot.

My other options are to just use the bike and try to keep an eye open for 20c tires. I do not want to run tubulars. And I don’t think that there is sufficient brake reach to convert the bike to using 650 sized wheels. Or just sell the bike frameset and move the components to a different frameset. Or sell the complete bike as is to a lighter beginner triathlete or time-trialist.

Just looking for opinions here, thanks in advance. I don’t have a good photo of the dropout without the wheel installed.

JohnDThompson 

I wouldn't modify a vertical dropout to get the clearance you need.

Convert to 650B wheels. You may need longer reach calipers, but those are available.

dsbrantjr

I think that if you remove enough material to move the wheel significantly rearward you will also remove enough material to make it significantly weakened and probably unsafe.
Converting to 650b is likely the only practical way to get bigger tires, but there will also likely be compromised braking with the longer-reach calipers required.
Tires often do not run true to size and it is possible that there are 23c tires out there which will fit; look for lighter weight tires, manufacturers often undersize tires to make them appear lighter for their stated size, or stick with the 20s you have found that fit.

treebound 

The older tires that were on the bike when I bought it were 23c, but were well beyond being safe.

I think I will start casually shopping around for 650b wheels and play with a conversion if I don’t sell the bike before then.

I wasn’t overly confident in machining the dropouts so I appreciate the consensus. Thanks.

blamester

First you have to measure it carefully and know how much you need.
But that looks tight in the photo.
And probably not a good idea.
Better stick with what you have or look at another bike.
No point fiddling around when you could probably get a more suitable bike with a little patience.

HillRider

If the 20c tires you found clear the frame like the previous 23c tire, it seems the new tires are the same size as the old ones despite the claimed size difference. Fitting 650b wheels and suitable brakes will be a significant expense and will lower the bottom bracket to the point pedal strike may become an issue.

I agree that you should either use the 20c marked tires or get a different bike if you really want to use larger tires.