Author Topic: 28mm tyres that aren't undersized - what exists?  (Read 2196 times)

28mm tyres that aren't undersized - what exists?
« on: March 03, 2017, 02:18:46 pm »
Wondering what ‘28mm’ tyres are available that actually measure 28mm wide (or slightly over) on Mavic Open Pro rims.

The various ’28mm’ tyres I’ve tried from Continental and Michelin all come up substantially undersized (by about 2mm in width, and even more in height – even on rims wider than Open Pros). Strangely, the anomalous ‘25mm’ Continental GP4000 measures 27mm wide – wider than a ‘28mm’ GP 4Season! Continental’s tyre-width labelling supremo must be blind – their ‘32mm’ Top Contact also actually measures 27mm, which thankfully was corrected when the Top Contact II came out……..but then again the ‘37mm’ Top Contact II Winter Premium is only about 32mm wide and 33mm tall, even on a wide touring rim, and slightly narrower than that on an Open Pro.

Since I’m trying to maximise tyre comfort on various bikes with limited clearances (to help cope with the incessant jolting and vibrations of virtually every yard of Britain’s crumbling road network), and these bikes will accommodate actual 28mm width tyres if they can be found, I would be interested to hear about others’ experiences of finding ‘28mm’ tyres that measure 28-29mm on Mavic Open Pros or similar rims. Most ‘32mm’ versions of such tyres seem to be much closer to their nominal sizes, so there is a huge 5-6mm actual jump from ‘28mm’ to ‘32mm’, with no obvious undersized ‘32mm’ tyres that might be squeezed in. Maybe there are some slightly undersized ‘30mm’ tyres knocking around out there?

I’m mostly interested in tyres of decent quality of the Grand Prix 4Season, Gatorskin, Power All Season type, although evidence on tyres from a range of applications (light/fast to robust/puncture-resistant) will be useful.

Thanks.

Re: 28mm tyres that aren't undersized - what exists?
« Reply #1 on: March 03, 2017, 02:30:15 pm »
I think the Rubino Pro comes up to quoted size, but it isn't as fast as the gp4season

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #2 on: March 03, 2017, 02:37:58 pm »
A Schwalbe Marathon Plus 28 is 28mm wide on my Mavic MA3 (similar width to Open Pro, I think).  Of course I do not recommend Marathon Plus for fast recreational riding, but I'd expect some other (if not all) models from the same manufacturer to be similarly proportioned.
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Re: 28mm tyres that aren't undersized - what exists?
« Reply #3 on: March 03, 2017, 03:41:18 pm »
My Pasela Tourguard 700x28 on Mavic comes in at just under 27mm width.

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #4 on: March 03, 2017, 04:15:40 pm »
Blodwyn (IIRC) liked Schwalbe Spicers which are nominally 30mm. There's a thread in the Reviews section
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Re: 28mm tyres that aren't undersized - what exists?
« Reply #5 on: March 03, 2017, 07:47:07 pm »
I've got a set of 32mm Marathon Supremes on one bike, and 28mm Michelin Pro 4 Endurance on another bike. Guess which ones are wider...

zigzag

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #6 on: March 03, 2017, 08:02:11 pm »
half-decent winter tyres - rubino pro 3 tech - in 28mm measure as 27.4mm on 17c internal rims; 28mm gatorskins were a bit larger iirc

Re: 28mm tyres that aren't undersized - what exists?
« Reply #7 on: March 10, 2017, 04:22:37 pm »
I think the Rubino Pro comes up to quoted size, but it isn't as fast as the gp4season

Interesting - more evidence of manufacturers' inconsistency, as I've seen others reporting they come in some way undersize.  Nothing surprises me when it comes to the accuracy and consistency of tyre width claims, both within individual and between multiple manufacturers!

Re: 28mm tyres that aren't undersized - what exists?
« Reply #8 on: March 10, 2017, 04:23:54 pm »
Thanks for the responses.  The quest continues.....!

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #9 on: March 10, 2017, 04:38:27 pm »
Could you go up to a 30mm? I think you'd like Schwalbe S-Ones. I certainly do :)

Road.cc tested them on 20mm internal width rims for 31mm true size. From searching t'interweb I think your Open Pros are quite a bit narrower at 15mm internal. It might be enough to make the difference?
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Re: 28mm tyres that aren't undersized - what exists?
« Reply #10 on: March 10, 2017, 05:38:02 pm »
Could you go up to a 30mm? I think you'd like Schwalbe S-Ones. I certainly do :)

Road.cc tested them on 20mm internal width rims for 31mm true size. From searching t'interweb I think your Open Pros are quite a bit narrower at 15mm internal. It might be enough to make the difference?

I think they come up about the same as 28mm One Pros, but with a bobbly tread. The latter are a good 30mm on 19mm internal rims. Apparently you can expect to gain/lose 0.4mm in width for each 1mm in internal width gained/lost - I've not tested this, but it came from one of the tyre manufacturers (and would only work properly for one size of tyre with a particular construction of course!)

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #11 on: March 11, 2017, 09:14:27 am »
I've got a set of 32mm Marathon Supremes on one bike, and 28mm Michelin Pro 4 Endurance on another bike. Guess which ones are wider...

Well my "25mm" Pro 4 Enduraces measure 27mm on my set of Open Pros, so I think I can guess :)
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Re: 28mm tyres that aren't undersized - what exists?
« Reply #12 on: March 11, 2017, 11:58:57 am »
28mm Conti Ultra Gatorskins = 25.8mm ::-) on a 17mm internal VO Raid rim

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #13 on: March 11, 2017, 01:30:59 pm »
Continental GP4000SII 28 tyres on rigida rims (19mm internal rim width) measure 30mm in lateral cross section and 28mm vertically from rim edge to rolling surface when pumped up to 110psi.
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Re: 28mm tyres that aren't undersized - what exists?
« Reply #14 on: March 13, 2017, 06:56:08 pm »
Just put the verniers across the 28mm Ultra Gatorskins on my audax bike with Open Pros and they are exactly 28mm. 
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Re: 28mm tyres that aren't undersized - what exists?
« Reply #15 on: March 13, 2017, 09:51:14 pm »
I'm running Marathon Supreme's in 28mm flavour at the moment and there definitely a lot narrower than 28mm.  Once spring is safely upon us I'll switch back to the Rubino pro 28s, they definitely are 28mm and are rather comfortable too.

citoyen

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #16 on: March 15, 2017, 05:20:47 pm »
I've got a set of 32mm Marathon Supremes on one bike, and 28mm Michelin Pro 4 Endurance on another bike. Guess which ones are wider...

Well my "25mm" Pro 4 Enduraces measure 27mm on my set of Open Pros, so I think I can guess :)

I've just fitted one of the 28mm Pro 4 Endurance to the new wheel I've built with a Stan's Grail rim and it comes up at almost 31mm.

On the Giant SL-0 wheels, they come up at 29mm.

To be fair, the Supremes are on Open Sport rims, which are somewhat narrower than either of the above. I should try them on the same wheels for a more accurate comparison.

Internal widths:
Open Sport 15mm
Giant SL-0 17mm
Stan's Grail 20mm

citoyen

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #17 on: March 15, 2017, 05:24:45 pm »
Road.cc tested them on 20mm internal width rims for 31mm true size.

Useful to know, thanks. I'm thinking of going tubeless and looking at S-Ones as a strong candidate for my money.

Re: 28mm tyres that aren't undersized - what exists?
« Reply #18 on: December 23, 2018, 05:54:27 pm »
Has anyone purchased '28mm' Continental GP 4Season tyres recently?  If so, how wide are they (and on what rim width and at what pressure)?

I've had many of these tyres labelled as '28mm' over the years, but all of them have struggled to get to 26.0mm wide, even after stretching from plenty of use, and even on a 17mm internal width rim.

However, I'm wondering if Continental has changed anything, perhaps in the last year or so.  This is because I saw in the wild not long ago a pair of GP 4Season tyres, labelled as '28mm' on rims I know to be 17mm internal width, and they seemed (looked and felt) enormous compared with all of my '28s' - not as large as 32mm GP 4Seasons, which are pretty close to or slightly over 32mm (so they weren't mis-labelled 32s), but definitely a lot larger than 26mm.  I didn't have measuring calipers with me, but I've handled enough 26-26.5mm GP 4Seasons for years on a variety of rim widths to know exactly how wide they feel by hand, and how wide they look.

I wasn't able to interrogate the owner as to the provenance of their tyres - hence the query about recent purchases that some may have made.

Of course, Continental has always been irritatingly untrustworthy in the labelling of its tyre sizes.  The '28mm' GP4000S II famously measures well over 29mm on a 15mm internal width Open Pro....but it seems, going by early reports, that its replacement, the new GP5000, is actually substantially narrower than the equivalent GP4000S II.

I'm still wanting GP 4Seasons that are wider than 26mm, but without having to make the huge jump to the 32mm version - so has Continental actually started making its '28mm' GP 4Seasons at the right size, or has this one-off sighting falsely got my hopes up?

Re: 28mm tyres that aren't undersized - what exists?
« Reply #19 on: December 23, 2018, 06:23:54 pm »
I'd have thought there would be more difference, in terms of comfort, between tyres of differing puncture resistance or quality of construction, than between those 2mm different in size.

Re: 28mm tyres that aren't undersized - what exists?
« Reply #20 on: December 23, 2018, 08:43:58 pm »
I purchased some 28mm Conti 4 Seasons just over a year ago.  After 7000k on Alexrims DF23 rims at 85psi they are 30mm width.  The rims are supposedly 16mm internal width although I measured about 15.5mm.  A somewhat older 25mm GP4000Sii of unknown mileage on the same type of rim measures 26.5mm at 100psi.

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #21 on: December 23, 2018, 08:51:24 pm »
I have a set of these in 28mm on my hack bike. They're fantastic, not a single puncture on them after months of hard riding around London doing deliveroo and they provide a good quality ride.

They were £10 each when I got them, sadly they're now more.

https://www.planetx.co.uk/i/q/TYVITREVG/vittoria-revolution-g-graphene-700c-wired-tyre
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https://yacf.co.uk/forum/index.php?topic=109048.msg2312359#msg2312359

Re: 28mm tyres that aren't undersized - what exists?
« Reply #22 on: December 23, 2018, 08:55:49 pm »
some tyres are just made the wrong size, no doubt about it. But FWIW some manufacturers make their heavier, more puncture resistant tyres using slightly narrower carcasses than their more lightly built ones.  The reason for this is that the tread can be rather thick, particularly  if there is a thick layer of puncture resistant material ( I'm thinking marathon greenguards, M+ etc in particular but also gatorskins etc to some extent).

Apologies if this obvious but the carcass of the tyre always ends up being round in cross section on the inside, which then leads to the tyre appearing to be 'tall' or not depending on the relative thicknesses of the sidewall and the tread.  Unless they build these thicker-treaded tyres on a slightly narrower carcass, they get folks complaining that the tyres are too tall and won't fit under the brakes of road bikes.  So 28mm marathons are never 28mm width, but they are often as tall off the rim as lighter built (and wider) tyres are.

Another issue is that the width of the tyre varies depending on the width of the rim.  Unfortunately if you fit the same tyre on different width rims, it isn't always predictable exactly how the fitted  width of the tyre  will vary.  Part of this is to do with how tall the lips on the rim are but there is also a fundamental issue to do with the bias angle in the carcass.  Basically if this is exactly correct the circumferential forces (hoop stresses that are trying to increase the width of the tyre) are matched exactly by the longitudinal forces, and the tyre stays the same shape regardless of pressure. But if the bias angle is different from that, one of two things occurs; either

 a) increased pressure causes the tyre section to get wider and the tyre to hug the rim more (assuming that the beads react to one another as per a tub rather than to the rim), which is what most tubs do or

b) increased pressure creates forces which are trying to make the tyre longer in circumference i.e. come off the rim rather than just wider in section. Most inner tubes do this (but for slightly different reasons) if you inflate them outside of the cover.


I think that the bias angle in carcass can tip from one state to the other depending on the exact rim width, hence tyres can vary in width in a slightly unpredictable fashion.  Also different width tyres are almost certainly designed to go on different width rims; for example Conti GP4000s in 25mm size may be designed to be 'size' on a 15mm internal width rim; they  usually come up between 26 and 27mm on a 17mm internal width rim but 28mm width versions of the same tyre may be designed to go a different width rim from the start (it would help if they made this clear) so usually don't come up +3mm width vs the 25mm tyre on any given rim.


A suggestion; there is lots of information out there, covering vast numbers of combinations of rim and tyre, it is just that none of it comes out of the woodwork until someone asks the question.  The sticky thread on tyre fit vs different rims is really useful; is is worth starting a thread in which we similarly measure the fitted width of various tyres on various rims?  We would need to indicate rim model, inner rim width, tyre size/model and approximate date of manufacture/purchase.

cheers

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Re: 28mm tyres that aren't undersized - what exists?
« Reply #23 on: December 23, 2018, 09:44:08 pm »
Has anyone purchased '28mm' Continental GP 4Season tyres recently?  If so, how wide are they (and on what rim width and at what pressure)?

I do, conveniently I got Vernier Calipers for my birthday so I don't keep nicking Dad's from his Scruitineering bag.

I use them on:
"28mm" - Mavic Kysyrium Disc - 17mm internal width
"28mm" - Hunt SuperDura - 20mm internal width
"25mm" - Shimano Something...

I'm not heading out to the garage in my PJ's but will give them a measure at various pressures... assuming I remember.

The 4 seasons certainly "appear" narrower than the 4000sII (which I don't currently have any on rims) and I've always thought the strengthened sidewall had that effect as the 23mm Gatorskin Hardshells I had years ago were way narrower than the other Conti 23mm tyres I had at the time (UltraSport and UltraRace)

I've also had 28mm GP4000SII and GP4Season's on the R500s that came with the Synapse, the brakes aren't spec'ed for 28mm tyres, and both of them were impossible to remove or fit with any reasonable amount of air in the tyres (but did clear a tab on the caliper... just); where as with the 25mm ones you could get them out without deflation but this is probably where most of my ripped tyre wall issues came from.  :-[

Re: 28mm tyres that aren't undersized - what exists?
« Reply #24 on: December 25, 2018, 08:36:23 pm »
some tyres are just made the wrong size, no doubt about it. But FWIW some manufacturers make their heavier, more puncture resistant tyres using slightly narrower carcasses than their more lightly built ones.  The reason for this is that the tread can be rather thick, particularly  if there is a thick layer of puncture resistant material ( I'm thinking marathon greenguards, M+ etc in particular but also gatorskins etc to some extent).

Apologies if this obvious but the carcass of the tyre always ends up being round in cross section on the inside, which then leads to the tyre appearing to be 'tall' or not depending on the relative thicknesses of the sidewall and the tread.  Unless they build these thicker-treaded tyres on a slightly narrower carcass, they get folks complaining that the tyres are too tall and won't fit under the brakes of road bikes.  So 28mm marathons are never 28mm width, but they are often as tall off the rim as lighter built (and wider) tyres are.

Another issue is that the width of the tyre varies depending on the width of the rim.  Unfortunately if you fit the same tyre on different width rims, it isn't always predictable exactly how the fitted  width of the tyre  will vary.  Part of this is to do with how tall the lips on the rim are but there is also a fundamental issue to do with the bias angle in the carcass.  Basically if this is exactly correct the circumferential forces (hoop stresses that are trying to increase the width of the tyre) are matched exactly by the longitudinal forces, and the tyre stays the same shape regardless of pressure. But if the bias angle is different from that, one of two things occurs; either

 a) increased pressure causes the tyre section to get wider and the tyre to hug the rim more (assuming that the beads react to one another as per a tub rather than to the rim), which is what most tubs do or

b) increased pressure creates forces which are trying to make the tyre longer in circumference i.e. come off the rim rather than just wider in section. Most inner tubes do this (but for slightly different reasons) if you inflate them outside of the cover.


I think that the bias angle in carcass can tip from one state to the other depending on the exact rim width, hence tyres can vary in width in a slightly unpredictable fashion.  Also different width tyres are almost certainly designed to go on different width rims; for example Conti GP4000s in 25mm size may be designed to be 'size' on a 15mm internal width rim; they  usually come up between 26 and 27mm on a 17mm internal width rim but 28mm width versions of the same tyre may be designed to go a different width rim from the start (it would help if they made this clear) so usually don't come up +3mm width vs the 25mm tyre on any given rim.


A suggestion; there is lots of information out there, covering vast numbers of combinations of rim and tyre, it is just that none of it comes out of the woodwork until someone asks the question.  The sticky thread on tyre fit vs different rims is really useful; is is worth starting a thread in which we similarly measure the fitted width of various tyres on various rims?  We would need to indicate rim model, inner rim width, tyre size/model and approximate date of manufacture/purchase.

cheers

I have seen somewhere, not on here I think, possibly on road.cc or from a manufacturer, an article explaining the normalised rim widths and inflation pressures for measuring  tyre widths. I think the tyres had to be a certain age, not new, before measuring to allow for tyre stretching. Possibly the article was from Mavic but I can't remember.