Any opinion on how wide tire I can run on a njs / keirin frame?
 

Hey hey bike friends
2nd time poster but an all- time browser here with a question for those of you who've ridden njs / keirin frame.

What is the widest tire you've fit on your frame? And have you had any problems fitting a wider than 25 tire on it??

I have a keirin frame built by a less known builder Umezawa. I believe it's built between 2000 - 2010. I heard that
keirin frames built in the 70s have comparably tighter clearance (could just be individual cases). But there seem to be some clearance on both front and drivetrain on my frame. I don't have a drilled fork.
I have been running a 23, but I ride in nyc daily and roads are ****. I have slipt into cracks and seams and fell a few times. I'm so done with the 23!
I know I could run 25 with no problems but ideally, I want to fit 28s on both front and rear. Thinking about running Continental Grand Prix GP 4000s on my velocity wheelset (cliche i know). I've measured to see if there's more than 3mm clearance but my measurement is ambiguous. There's like a little less than 3mm from tire to fork on both sides.

Does anyone have any insight/ experience on this?
TY!!

This is why people who ride on bad roads make smarter bike choices. :lol:

Don't get me wrong I love riding it on the road and I'm not done with tracks bikes on the road yet.
I've ridden a few tracks bikes in the city and this njs frame is by far the most fun. :fred:
Just looking for opinions from people with similar experience otherwise back off :love:

Hey, you gotta be careful when you ask for "any insight". ;)

The best way to know what you can put on your frame is to measure the clearance around the tires you have. I like to use allen wrenches as feeler gauges. Let's say you have 23mm tires on now, and you can slip a 3mm allen wrench in between your front tire and the fork crown. Well, since tires are roughly circular, that means a 25mm tire would be about 2mm taller, and an extra mm on each side. Probably not enough clearance for a 28mm in this example though. Rear tire is much the same, except you have to keep an eye on the chainstay clearance too.

Unless there is an NJS/keirin spec for tire clearance, it's very possible for two track bikes to have different tire clearances, so the size of tires someone else can fit may not be applicable to you...

It's really quite frame-specific. How much clearance do you have at the rear stay bridge and the fork crown? That's what will determine how wide a tire you can fit.

N.B. be aware that the width designations on tires tend to be "nominal" rather than "actual," at least in part due to the fact that rim width can influence mounted tire width.

To easy.

who tf is racing keirin on 25c tubulars?

Seriously doubt your NJS bike is going to fit 28s.

Measure once, cut twice!

Update
 

Update after a year re my njs tire clearance (rear spacing is 120)
Front tire clearance up to 25mm, on the rear I was able to run a 28mm RibMo tire

Do a 650b conversion, fit at least 34 maybe 38. Just watch for pedal strike