I've never been able to fit gp4000 28 on a rim brake bike, never had a problem on a disk brake bike. As has been said the brake calipers limits you more than the frame.

That's really interesting about the brake calipers, and something I hadn't really considered. I do know on my 2012 R3, the GP4000 28mm didn't have an issue with the calipers(ultegra 6800). It would fit, but like I said, I got frame rub as soon as I stood up on a hard effort. I kinda wanted disc brakes anyway, so I guess that's another factor to look at..

I have also run 28mm GP4000 with 23mm rim on a 2013 Venge. Not much clearance though.
A friend with Venge Vias Disc tried them. They fitted on the back but not the front.
On my Madone 9.5 they also fit but tight clearance to the seat tube so I won't run them as it will get scratched up with road debris.

I can't imagine they would fit.

I have a 2010 S1 with Flo 30 wheels and run GP4000 in 23. I have the stock brakes and just leave them open and things clear. Maybe a 25 would work but it would be close. 28? I don't see how it could.

How long is the trail? I rode it once years ago but can't remember the length. Would you feel comfortable riding GP4000's on the john wayne trail up to Snoqualmie pass?

Cannondale Synapse Disc. I can run Clement Strada 32s on there with no problem. I used it for road and some rails-to-trails and it was amazing.

I just picked up a Santa Cruz Stigmata.

I have been riding on and off road on 33mm maxxis mud wrestlers while waiting on another wheels set to mount some sector 32 Hutchingson tires.

Disc not calipers and running tubeless, hence two wheel sets.

I am setting all sorts of PB's on Strava segments even on the nobby tires.

I am convinced that if you are not a tiny human (the type that would fit in my pocket or could be put on the top of a wedding cake) that 32+ tires at 40 - 50 psi are way faster than 23's at 90 - 95 psi.

2018 3T Strada doesn't just fit them, it comes with GP4000IIs in 700c x 28mm.

-SD

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https://www.kickstarter.com/...bike-for-the-new-era

Canyon Endurace SLX comes stock with 28mm GP 4000s II and can fit 31-33mm tires from what I have read. They are supposedly going to be available in the US next month per their email, but I'm not holding my breath.

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Matt

John Wayne trail on a road bike with 28 slicks? I wouldn't. That's a proper gravel trail. Road tire might be okay in the wheel ruts where they exist, but leave them and you'd hit deep loose gravel.

Part of Snoqualmie trail that I've seen (Carnation and Fall City area) is mostly covered in fine sand and dirt and it'd be probably fine with 23s although I'd feel more confident with 28s. The trail is 19 miles long from Duvall to town of Snoqualmie, then it disappears through Snoqualmie, then reemerges again for another 10 miles to rattlesnake lake. The gap is bikeable (Tokul, 396, Reinig). You'll be riding right past the Twin Peaks sign there. :D

I have a 2014 R3 with the fulcrum rims what 28mm will fit?

You're probably going to just have to try out different tires and return the ones that don't work.

There were multiple iterations of the GranFondo: alloy, carbon, and premium carbon frames; some with rim and disc brake versions. I have a GF02 carbon rim brake frame. I'm running 25c Michelin Pro 4's on 15c rims. There's not a lot of room left, especially at the rear brake bridge. I'd be shocked if any 30c tire would fit without rubbing. I've been contemplating getting a set of 28c Turbo Cottons, but am not sure they'll even fit. Plus I already have a hard enough time getting the 25c tires through the brake calipers. With the narrow rims, I'd probably have to unbolt the brake cable or deflate the tire every time the wheel had to come off.

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"They're made of latex, not nitroglycerin"