t2p

Have 25mm GP 5000 tires on an old Schwinn Peloton with Kinesis alloy fork ; Ultegra dual caliper brakes (1990's)

The tires measure around 24mm installed (Campy Omega 19 rims)

Considering 28mm for the next set - but 28's might be too large ?

Appear to have room in the rear - but fairly tight at the front (fork)

Do the 28's measure at 28mm - or possibly less or more ?
.

SoSmellyAir

How wide a tire measures also depends on the internal width of the rim and tire pressure. When I first installed a 25 mm GP 5000 onto a Mavic Ksyrium Elite wheel with an internal width of 17 mm (i.e., ETRTO 622 x 17C) and inflated it to 90 PSI, the tire measured barely 7/8" wide. After several cycles of pre-ride inflation to 85 PSI and riding, for a total of roughly 200 miles over the course of about 3 weeks, the tire expanded to its nominal width and has stayed that way since then.

SpedFast

I have 25mm's that measure 27mm and I have 28mm Vittoro's that measure 30mm. I also have some Kendra 32mm's that only measure 30mm. All dimensions taken with calipers on tires inflated to max pressures with many miles on them. The 25 and 28's are mounted on 17mm rims and the 32's are mounted on 19mm rims. I find I have the least clearance not side to side but between the mounting bracket for the Front DR on the one, and between the front brake calipers pivot point and the tire on another. The difference in comfort between the 25 and 28 is like night and day FWIW. Also, different tires from the same mfg measure slightly different. Unless you have a few mm's of spare clearance on each potential contact point on the 25's you have mounted now, I would be leary. The only time I have a problem with my clearances is if I run through mud or pine needles, wet leaves, anything that sticks to the tire quickly jams things up. Sometimes to the point of having to stop and scrape the crap out before continuing my ride. HTH

sean.hwy

On my aero road bike systemsix it was not the width but the height the was really close. 23/25mm fit great. The gp5000 28mm just barely fit in the back by the seat post.

several of my photos around post #20 and #25
https://www.bikeforums.net/road-cycl...0mm-tyres.html

SalsaShark

I tried fitting 28mm on a 2000 Peloton Pro I had for awhile, and while I can't remember if it would clear in the rear, I am sure it would not clear the fork or front caliper, which was an ultegra on a carbon Look fork with steel steerer if I remember correctly. Had to stick with 25mm tires on that one.

biker128pedal

For GP5000 may depend on when it was made and the specific flavor. I’ve got one about 2 to 3 years old. On a 19mm inside width Aeoles at 90psig it measured 29.0 mm. Note it gets taller but this l did not measure. I’d run 25 from and 28 rear.

znomit

If the rear will fit then buy one and try it on the front to see, No harm in mix and matching.
They run smaller than the GP4000, but remember if it's tight and picks up a stone you can shred your tyre.

t2p

25 does appear to be the max