p00kaju

Hello.

First post. Can't find answe using search propably just not using it right

Just bought GP5000 S TR 28mm (front) and 30mm (rear).

Installed them for my new Nextie aero wheels, hooked and inner width 24mm.
Tubeless installation and pressure approx 4.5 bar.

After first 100km tire actual width measured in front little under 31mm and rear 33mm.

I bought this model because many review says that this S TR is more true to size than older models but seems that it's not true.

Could there be difference between batches or is this common with extreme wide wheels?

Iride01 

Stated tire width by the manufacturer doesn't include the rubber on the outside of the casing is what I always heard. As well the pressure you pump them up to will make some difference.

I really don't care whether the tire is it's stated size or not. If it fits in the bike frame then I'm happy. If not, I get the next smaller size if I'm going to use the same brand and model.

Welcome to BF.

p00kaju

Manufacturer gives max real tire width 32mm and 33mm seems to leave enough clearance.
So that is not problem and tires feels very nice.

Just curious that could there be any variation between patches.

Iride01 

Patches? You mean skid patches?

Or are you asking if there is variation between production runs (batches) of that model tire? If so, I would think there are variations. How much? Probably not much normally, but sure at certain times there might be something more than one might want.

p00kaju

Yes I mean batches. Bad English skills and not using google translate = 🙈

PeteHski

Maybe 24 mm hookless internal rims are a bit wider than their reference. My DT Swiss rims are 22 mm hooked. I’ll measure the tyres and see how close they are to the stated 30 mm. I also run the S TR at around 4.2 bar front and 4.5 bar rear.

alcjphil

Bicycle tire width has always been amorphous. Rim width has always affected overall measured tire width. My example: I am riding Hutchinson Fusion5 700 x 28 tubeless tires on Campagnolo Shamal wheels which have an internal width of 17 mm. They measure at exactly 28 mm wide. I am sure that with a wider rim they would be wider, but my Look 595 probably wouldn't be able to accept anything wider. Unless your bike has no room for anything wider, why worry?

mstateglfr 

95% sure Conti used a 19mm internal with rim for their gp5k tire widths.
So if you have a 24mm internal width rim, the tires will measure wider than stated.

Mtracer

My GP 5000 S TR 28mm tires measure 31 mm wide on my 25 mm wide internal rims. This is after a few thousand miles. I think they were just a hair over 30 mm when I first put them on. Exactly what I expected based on rim manufacturers data. Wider internal rims will get you a wider tire width. 24 mm rims (as is my 25 mm) is very wide for 28 mm tires. Maybe not the limit, but close.

That's the problem with stated tire widths, while it means something, it's not necessarily what you will get on your rims. I doubt any tire spec'ed at 28 mm will be anywhere close to 28 mm when put on such wide rims.

Sy Reene

A set of data below. This suggests that the 28mm nominal size = actual size when on a 18mm ID rim. I think that it hasn't changed much in that a tire's size is determined/labelled based on using a rim roughly 2/3 of its size.

https://www.bicyclerollingresistance...-tr-comparison

msu2001la

As others have stated, 24mm internal is pretty wide and will likely result in actual tire sizes wider than what is printed on the tire. This isn't specific to Continental tires.

p00kaju

Thank you for all the answers. So it is normal that tires expand with my extra wide rims.

Glad that my frame allows this wide and now I will start enjoying my wicked fast and comfortable tire 💪

Mtracer

A simple way to look at this is the cross section of the tire and rim form a loop. The wider the rim, the more of the loop is made by the rim and the loop gets large. Since this loop is more or less a circle, the larger loop (circle) will have a large diameter (tire width).

And yes, those are fast tires, I use them myself. Enjoy.

tFUnK

Not batches per se, but different release generations, sure. I've got older GP4Ks that mount up to 23mm tims (OW) a bit fatter than labeled, and newer versions of the same model that mount up true to size on the same rim.

In your case, the 24mm IW rim is quite wide (maybe intended for gravel?) so a road tire would mount up fatter than expected. I'm willing to bet a beer that your tires will mount true to label on a 23-25mm OW rim.

rm -rf

The older GP4000 (and GP5000?) in 25mm measured wider. Newer ones seem more true to size.
On my 20.5mm ID rims:
25mm: 26.5 to 27.0mm
28mm: 29mm. More true to size now.

~~
Tire pressures
I would use your actual 31mm and 33mm widths for deciding tire pressures.

Air volume goes up proportional to the square of the radius or diameter. (Since a round cross section area is " pi x r squared" )

28mm vs 31mm is around 20% more air volume! Smooth!

Sy Reene

I would like to know how or who adjusts tire pressure though, with taking inflated height into account as well? 2 different tires, 'only' showing a 1mm difference in inflated width, but actually a 3mm difference in height.

GhostRider62

The casings are different. One is tubeless and the other isn't.

Who or how does one compare Apples to Oranges.

Tire width does not change as much over time with the GP 5000 S TR compared to the old GP4K, which got plumpier and plumpier. The old 28mm would eventually run a hair over 32mm for me whereas the S TR is 29 mm and they stay fairly consistent. If you need to adjust pressure for a tire to fit your bike, you need to run smaller tires

PeteHski

Some of the pressure calculators are based on your actual measured tyre width and some are based on nominal stated tyre width, along with internal rim width. But they are both approximations as they rarely cater for specific tyre models and I don’t know any calculators that include tyre height as a specific variable.

But in any case they are just a guide to setting tyre pressure and usually get you in the right ball park.

Sy Reene

I guess so, but at the same time I'm thinking how different these 2 tires's sizes could be considered different if you think of the shape as more ovalized.
Nominally, you could quickly (incorrectly) think a 27mm inflated width tire is only 4% greater in size than a 26mm tire, but with an ovalized area and the height differential, it grows to perhaps about a 12% difference. Since the various tire pressure calculators don't include height, the ballparks can be quite large in size.

PeteHski

I guess that's the value of knowing the height when comparing tyres of the same width.

urbanknight

According to the ETRTO standards someone educated me with recently, your 28mm tire should be sized for a 19mm rim and the 30mm for a 21mm rim. So a 24mm width would have the tire measuring noticeably wider.
https://www.vittoria.com/ww/en/stori...rto-bike-tires

PeteHski

The trouble is that not all tyre manufacturers are following the latest Industry standards. Some are still playing catch-up and I think that’s what happened with the latest gen Contis ie they moved to the new standard as you quoted.

GhostRider62

I posted actual widths of 25, 28, 30, 32mm Conti GP5000 S TR mounted on 25 mm Zipp 303 hookless Firecrest rims and some data on 21 mm hooked Reynolds rims.

26, 30, 33, and 35mm for the Zipps and 25.5 and 29mm for Reynolds, approx.

p00kaju

Nice. Sounds about the same as mine with 24mm ID.

eduskator

24mm inner width. There's your culprit. They're most likely true to size on narrower rims like 17mm or 19mm.

On my current wheels (hookless / 22.4mm inner width), my 25mm measure 28mm when inflated and my 28mm measure 30mm.