Anyone gone large (28mm tyres)

[Milzy]

28 tubs and average speed is up by 0.8mph.

 

[Huggis]

Hey all not sure if this thread is still alive. I posted earlier and ended up plumping for 28mm GP4000 for my Fulcrum Racing Quattro DB wheels. Now the interesting fact is that these measure nearer 31mm (30.5-30.7mm). The ETRO on the tyre are both 622 and the recommended tyre width is 28? However there is a bit of a 'light bulb' effect. I measured the 25mm GP4000 on my other bike and they came up at 26.5mm. Thinking about going down to the 25mm..

 

[Flick of the Elbow]

The brands vary considerably in their actual width. Michelin Pro 4s in 25mm measure nearly 28mm, for example.

It also depends on the width of the rim. The same tyre on different rims could measure different widths.

 

[keithmac]

I run 700×35c at 35 psi wouldn't fancy anthing smaller than that, would knock my teeth out!.

 

[Huggis]

It also depends on the width of the rim. The same tyre on different rims could measure different widths.

Yes but if both are ETRO 622 surely the width should be as specified? Can't think of any other area of cycling where such lose tolerances would be accepted.

 

[fatjel]

I recently swapped my Kaffenbacks frame for a London rd so I could get 35 tyres on
Is a very definite comfort advantage over the 28s. (both marathon greenguards)

 

[Ming the Merciless]

Remember the old 27" x 1 1/4 inch tyres on your 10 speed Raleigh of the 80's? Well that's 32mm in modern money. Wider tyres are just back to the future...

 

[Ajax Bay]

but if both are ETRO 622 surely the width should be as specified? Can't think of any other area of cycling where such lose tolerances would be accepted.

It also depends on the width of the rim. The same tyre on different rims could measure different widths.

622 is the diameter and rims will have a inner bead width shown. Tyres eg 622-25 will nominally measure 25mm wide but rim inner bead varies and that variation causes a difference in the actual tyre width (at the same pressure). It's not an issue of "lose (sic) tolerances", it's physical reality, as Flick has already said (though it's not 'could', it's 'will' (measure differently)).

https://www.cyclechat.net/threads/n...hts-to-return-them.202764/page-2#post-4334295
Measuring the width of the new Continental GP 4 Seasons 28-622 I'd just mounted on 622-15 Mavic MA3 rims (NB 15mm inside bead) @ 100psi was 26.1mm.
@andrew_s 's measurement on 13mm rims @ 100psi was 25.7mm.

 

[Richard A Thackeray]

I specified 28s on my new (in March) bike
It's a Ribble CGR, so would look silly with anything narrower

My previous work/general purpose/'training' bike (which the CGR will supplant) was one of the Ribble 'blue winter/audax' frames, that would only accept 23s with mudguards
The size still came as a shock, & felt dreadfully slow to begin with, allied to the higher (front end) position
It's a double-edged sword, as they're more pothole resistant, & also okay on dry bridleways (bigger air-chamber, for tree-roots)
That said, they're probably the biggest tyres I've used since (1.25") slicks on my Pace Research, back in the mid-90's!!

The 'Blue', & my (Ribble) Gran Fondo will both remain on 23 though

 

[Ajax Bay]

felt dreadfully slow

Can you quantify how much slower this bike with 28s on is compared to your 'blue' (say) on 23s?
Do you associate vibration frequency or amplitude with speed?

 

[Foghat]

Bearing in mind, of course, that Continental is pretty inept at maintaining consistency in applying its nominal tyre width figures to its tyres' actual physical dimensions.

See the following for an idea of the extent of variation, all on the same Mavic Open Pro rims:

GP4Season '28' - 26.3mm
GP4Season '32' - 32mm
GP4000 '25' - 27.5mm
GP4000S '28' - 31mm
Top Contact '28' - 24.5mm
Top Contact '32' - 27.5mm
Top Contact II '28' - 28.5mm
Top Contact II '32' - 31.5mm
Top Contact II Winter Premium '37' - 30.5mm

'28' seems to be particularly problematical for Continental's tyre-size-labelling supremo, with actual widths varying from 24.5mm to 31mm. This is absurd and completely unhelpful when you consider that (actual) 28mm is hovering around the optimum size for fitting the widest (sensibly) achievable tyres to 57mm-drop rim brake frames with mudguards (and many 49mm-drop brake frames without mudguards).

 

[Richard A Thackeray]

Can you quantify how much slower this bike with 28s on is compared to your 'blue' (say) on 23s?
Do you associate vibration frequency or amplitude with speed?

It had essentially the same gearing (barring a couple of lower sprockets)
50/34 chainsets on 'blue' & CGR
12-25 on 'blue', & 12-28 on CGR

It was the drag factor, even at high pressures, may it was psychological, as it feels okay
Still slower uphill, but it is a lot heaver

 

[smutchin]

It was the drag factor, even at high pressures, may it was psychological, as it feels okay
Still slower uphill, but it is a lot heaver

Yeah, very possibly psychological. It's hard to quantify these things objectively as there are so many other factors to take into account. Personally, I don't find 28s noticeably slower than 25s.

 

[Drago]

28's on my Dolomite don't return notably different route times to the 23's on my F75. I would guess the aerodynamic effects of the mudguards make a much greater difference.

 

[smutchin]

Remember the old 27" x 1 1/4 inch tyres on your 10 speed Raleigh of the 80's? Well that's 32mm in modern money. Wider tyres are just back to the future...

TMN to...

Remember, for years and years, the most common British road bike tyre was 27x1¼", which is 32mm wide (unless you're Schwalbe, for whom it's sometimes 28mm). It wasn't without some justification IMO. I'm still riding them

I remember turning up to my first ride with a local club on a bike with 27 x 1 1/4 tyres and being treated with some scorn. That was around 10 years ago. I never rode with them again. They're probably all on 32mm tyres now.