Been on 32mm a few years now, it’s like going back to the width in the 1980s for the UK at least. I don’t race, and my average speeds have not declined from when I ran narrower. It requires so much less energy to ride when you have that extra volume air cushion. Narrow higher pressure tyres feel faster but in reality on the road are not. Leave that to velodromes.
I’ve just acquired some GP5000 S TR in 32 and will be fitting them tonight for a test tomorrow. They’re going on 303 Firecrest, so I’m guessing they’ll run to 34 or so. I’m hitting 110km tomorrow so that’ll be a decent run out. Will report back!
Fitted. One went on very simply (1 tyre lever used, but stronger thumbs than mine wouldn’t have needed it, and inflated first time with a track pump), while the other was a little harder to inflate, but after a little fiddling with the bead it was fine.
Weight difference vs the Pirelli P-zero race tlr in a 28 is very unscientifically ~20g; the whole wheel unit has come up c.40g heavier, but I’ve topped up each wheel with an extra 20ml sealant. This corresponds pretty accurately to Pirelli’s claimed weight of 295g and Conti’s claimed 320. In any case, they’re trivially heavier.
They’ve come up just shy of 34. Just over 5mm clearance left up front, just about 4 at the back. I probably wouldn’t want to chance anything bigger at the back - the seat tube gap is the narrow point.
Have fun on those balloons tomorrow
Ok, so that was interesting. First, the GP5000S TR is a fast tyre. It has that really zippy feeling that only real race tyres have. It seems (stress ‘seems’) a faster tyre than the P zero race. That, though, is probably a function of the tyre more than the width.
I also experienced a bit more confidence and grip descending, but perhaps that’s partly due to the slightly warmer and drier roads we’re now getting in the Chilterns after a run of fairly warm and dry weather (for February). I did hit a PR down a hill I’ve ridden dozens of times, mind you, and that’s surprising for winter.
Comfort is definitely slightly improved but I don’t think it was a game changer. I set the pressure to 48 psi rear, 45 front, and actually think the sweetspot might be 2-4 psi below that (for reference, I’m 70kg/154lbs, and the tyres are mounted on Zipp 303 Firecrests).
For those interested, today’s numbers:
98.6km, 28.6 kph av speed, 198w av power, 219 NP, av HR 143, weather impact 1.3%. The objective of today was (after getting warm) to try and ride 3 solid hours right on my perceived VT1 and really minimise coasting.
Last long ride: 103km, 26.0 av speed, 188 av power, 202NP, av HR 135, weather impact 5.8%. This was a 60km potter with a friend followed by 40km solo ‘pressing on’ (low tempo).
In other words, the rides are too different to compare the data.
I’ll keep posting in here with reflections as I get more miles out of the tyres.
How much climbing on each of those rides?
~950m today, ~1100m last week.
Isnt there a trade off here in lower pressure higher rolling resistance?
Here is a tire tested at various sizes.
I just bought a new bike and was going to be going to 32s… was previously on 28s…is it really worth dropping air pressure so low if you are riding on the road? It just seems like we can get some more comfort in going to a larger tire size regardless. I cant ride outside yet to test…too much snow. Will test eventually.
Sensible question. My view is that I’m not racing (semi-competitive sportives are as close as I’ll likely get), so a handful of watts doesn’t matter, and if I can get more comfort and grip and still have a fast tyre, it’s a win/win.
At 44psi, BRR puts the GP5000S TR (in 32) at 12.8w. That’s just below the pressure recommended for me by the SRAM tyre pressure calculator (and as established earlier, 48/45 is probably a bit high). At 60psi (the calculator recommends 62/58), BRR has the P Zero Race TLR at 16.9W.
Now while the absolute numbers don’t matter, (and I couldn’t run the 26 on the 303FC anyway) that does seem to corroborate the idea at the GP5000S TR in a 30/32 will be faster, grippier and more comfortable than a 26-28 P Zero.
If I were at the sharp end of racing I’d probably put 28 on the front and 30 on the back, but for my current use, 32s (or 30/32) seem right. But it’s very early days.
Don’t forget the trade off in aero and size.
I also didn’t find larger tires to be a game changer. I’ve tried 26-35mm width as measured tires. Road feel is more important.
Higher volume tires (32c) does appear to reduce flats on rear tire.
My plan is to try 44/41 next week and go from there. 48/45 didn’t seem way off, just a bit high.
Does anyone have tire width measurements for 32mm GP5k TR on ~22mm internal width hooked rims? I suspect they’ll inflate true to size since 22mm isn’t really out of the ordinary anymore.
I’m currently of the train of thought that better surfaces and faster speeds exert a downward pressure on the optimum tyre size, while poorer surfaces and slower speeds point towards wider ones.
In my case, the semi-rural roads of Herts, Beds, Bucks and Oxfordshire are often quite poor in quality. In the summer, I might average 35-37kph if I join the A group for some evening loops, but most of my riding is going to be in the 28-32kph range. My understanding of the current thinking is that in that 28-32 range, there is likely to be little to no speed difference between a 28 and a 32 (probably even a 35 if it would fit), but there will be advantages to the wider tyre in grip, comfort and puncture resistance. In the paceline, there probably are small aero losses, but it’s such a small part of my riding, it’s not worth worrying about.
Others may have different views and that’s totally cool, but IMO when you’re quick enough to worry about these kind of differences (like the AXS 10t argument), you’re probably quick enough to be riding what your sponsor gives you (or at least heavily subsidises). Even on that note, the fastest rider I know is planning to be on 30s this year…
I wouldnt mind hearing how you find it. I typically wont get to ride outside till late April so lots of time for me to dwell on it.
A random gripe but I kinda don’t like Zipp’s new logo 
If it helps, that chimes pretty well with my experience on the equally poor road surfaces of Surrey and Berkshire! Over last couple of years I’ve run various bikes and wheelsets with tyres from 25 to 32mm and 45 to 90psi. If it’s a cruisey 28-32kph ride (solo or group) then I’ll take wider and lower pressure every day of the week, there’s no noticeable downside and if anything maybe a speed benefit on rougher sections or if the ride is long enough that the increased comfort leads to less fatigue.
But I also race and do fast group rides (on routes chosen for good road surface) where the average will be 40+kph, and in those cases I definitely find a noticeable penalty from wide and lower pressure tyres. I think the optimum for riding fast on decent UK surfaces would be 28s (or maybe 28 front, 30 rear) run at the higher end of the recommended pressure, on wheels with wide enough rims (30+mm) to adhere to the 105% rule for a good rim-tire interface. Unfortunately I don’t currently own a set of wheels with rims that wide! My widest rims are 27mm and with a 28mm tyre it does noticeably bulge out wider than the rim. So I tend to race 25mm unless I know it’s a course with bad road surface in which case I might use 28mm (or just not enter…).
Whats the max size anyone has managed to fit to an SL7?
From another thread I wrote this:
I’ve got an SL7 and no problem with 32c tires that on wider gravel wheels measure out to 34-35mm. I’ve used both Pirelli Cinturato Velo TLR in 32c (measures out to 34mm) and Specialized Roubaix Pro 2Bliss 30/32c (measures out to 35-36mm). Measured width on Roval Terra gravel wheels with 25mm internal width. The easy gravel out here is mostly dirt roads with some rocks.
After about 500 miles the Roubaix expanded a bit more, and while riding to pick up my bib for an event I stood up to get thru a traffic light and 800+ watts made the tire rub against the chain stay.
Had 3-4mm of clearance at chain stay after initial install of Roubaix when they measured at 36mm.
BicycleRollingResistance measured the Roubaix Pro 30/32 at 31.9mm on wheels with 17.8mm internal width. They measured 36mm on my Roval Terra wheels with 25mm internal width. Basically 32mm on old school wheels, and 36mm on wide gravel wheels. Pretty big difference.
I have been running Challenge Strada Bianca for the last year or so. I have 2 sizes, 36mm and 45mm. I got the 45s on the bike when they were released and now I no longer ride my 650b bike. In fact it is now my trainer bike (used to be my primary)
I don’t know if I will fit the 36s this year unless I end up doing STP and even then I might leave on the 45s. the 45s work exceptionally well on road and gravel. I keep up with the folks from my cx team on team gravel/road rides.
I ride a 56cm Lynskey GR270 with titanium fork