What's happened to my tyre?

Reidy

Member
Apr 17, 2023
7
3
Moray
When giving the bike a good clean, noticed cracks have appeared around upper walls of tyre. Any idea how this has happened, and more importantly is it time for the bin? They're only about year old, maybe 1000mls of mixed trails.
As seen on photos it's a 3inch front tyre, running on a 30mm wide rim with Cushcore inserts. Running with anything from 15/20 psi depending on ride.

IMG_20240601_134654.jpg IMG_20240601_134706.jpg IMG_20240601_134712.jpg IMG_20240601_135009.jpg
 

The Hodge

Mystic Meg
Subscriber
Sep 9, 2020
3,800
7,881
North West Northumberland
Loads of tread on there still..never seen that before in terms of the " cracks"..
Is there any significant loss of air between rides ?
If not then I would still run with it ..but that's me.. a tightwad ..and not a recommendation.
 

xtraman122

New Member
Mar 2, 2024
76
37
USA
Any chance you use any chemicals for cleaning that may have gotten on there? I know car tires can do this if they get too much tire shine on them from repeated use. Other thought was if they had gotten a lot of sun exposure that may have just been taking a toll.
 

Reidy

Member
Apr 17, 2023
7
3
Moray
Not loosing any pressure and live in NE of Scotland, so that rules out overexposure to sun and the bin! Cleaned sidewalls of both tyres once with cloth that had excess plastic restorer(thrifty I know), but rear tyre fine.
 

steve_sordy

Wedding Crasher
Nov 5, 2018
8,680
8,948
Lincolnshire, UK
@Reidy There is a very good chance that the tyres are too wide for the rim. Combined with low pressure, this leads to ballooning and excess stress on the tyre walls. Hence the cracking that you see.

Here is a link to a very useful WTB site on tyre widths vs rim widths.
Tire & Rim Fit Chart

Page down a few times until you get to the charts. The second chart is the one you need. The chart shows recommended combinations of inner rim width and tyre width, all in mm. Your inner rim width is 30mm and your tyre width is 76mm (3").
That combo is off the chart. For optimal performance, the max tyre width for that rim width is 2.6"

However, it may also be a manufacturing fault. The tyres are in good condition (they still have the moulding fins!) and the blocks are all still sharp. It would be worth contacting the tyre supplier and sending the photographs to them (make sure that the tyres are CLEAN!). There is no need to mention the mileage, let the photos speak for themselves, but they will need to know how old they are.

Note: I had a similar problem on two separate occasions. Each was the exact same tyre brand/size/type, but bought from different countries. In my case, the tyres actually split open at the bead! That was after about 700 miles, but like yours, the tyres looked almost new (a benefit of forest riding). The first time, I thought it was just bad luck, but the second time I suspected a manufacturing fault because both tyres had split in the same place in relation to the logo. I got a 100% refund without a problem on both occasions.
 

Mikerb

E*POWAH Elite World Champion
May 16, 2019
6,292
4,784
Weymouth
Agree with the a bove. The tyre should be on a 35mm rim width. That combined with running pressures too low means the tyre is completely out of shape and not performing as designed. Ideal mtb tyre width for a 30mm rim is 2.4/2.5. In my experience even 2.6 on a 30 rim is vague and unstable.
 

Hiltix

Member
Mar 28, 2023
27
50
Bern, Switzerland
In addition, possibly caused by the Cushcore in combination with low pressure, the bending radius when pressure is applied to the tire is smaller than usual and thus leads to the cracks shown.
 

xtraman122

New Member
Mar 2, 2024
76
37
USA
Do you have the big eMTB style Cush cores? I bought them and they stick out super wide off of the rim so I can see why they’d encourage what others above are saying.
 

Stihldog

Handheld Power Tool
Subscriber
Jun 10, 2020
3,179
4,407
Coquitlam, BC
I was able to fit a large CushCore in the rear tire. 35mm rim and 2.6” Assigia.

35mm wide rim works well with a 2.6” tire. It’s a must for 3” tires IMO. Maybe even a wider rim. 40mm? The larger CushCore will easily fit.
 

2WheelsNot4

E*POWAH Master
Oct 17, 2021
904
700
Scotland
Cracked = bin.

Its going to delaminate from the backing, so theres a chance a section will come away in use, leading to tyre failure.
Basically its going to be like getting a puncture, so not really dangerous, but it will spoil your day.

Tyres are cheap enough these days so save on a headache and just get shot of it

Being a pretty new tyre though, maybe send a pic to the manufacturers, and they might just replace it.
 

Reidy

Member
Apr 17, 2023
7
3
Moray
Thanks for feedback lads, the rim to tyre ratio looks to be the problem. As rear tyre only 2.6 wide and fine. I’m not an aggressive rider, so not feeling it unstable, but did notice a smoother ride when increased width.
Will probably go back to 2.6 both front and rear, which bike came with from manufacturer.
I’m using the Cushcore E-MTB set.
 

ari

New Member
Mar 1, 2024
37
18
Australia
I have a 2.60 Mitas tyres that have similar cracking going on , and some areas look like someone has slashed with a knife. It was suggested that someone was too liberal with the release agent in the mould , making the surface weaker , but all the rubber is still there on the inside .[what ever all that means :)
 

rzvrazvan

New Member
Oct 13, 2023
1
0
Ploiesti
I just installed a 2.4 DHR II instead of a 2.5 on the rear wheel with a Rimpact EDH insert and yes the wtb rims are 30mm wide and go with 2.4/2.5 from the 2.6 you need an inner rim width of 35mm!

IMG_20240706_132627.jpg IMG_20240706_163149.jpg
 

Stihldog

Handheld Power Tool
Subscriber
Jun 10, 2020
3,179
4,407
Coquitlam, BC
I think 2.6” wide tires are the turning point between 30mm rims and 35mm rims. Either width of rim will work fine. But now it depends on CushCore size, amount of psi you typically use, type of terrain you want to ride on.

On one bike I use 2.6” on a 35mm rim with a large CushCore (barely fits). On the other bike 2.4” on a 30mm rim. Regular sized CushCore. I adjust the psi according to conditions (snow, mud, loam, rock …etc.
 

20mph

Member
Subscriber
Jan 30, 2024
18
45
Leeds
Hey mate, looks like your tyre's knackered from old rubber and too much sun can happen with age and UV rays. That make rubber crystallises, loose grip, make much more stiff and cracking. There's a few other reasons too: Stuff like ozone, extreme temps and humidity can make the rubber degrade faster. Heavy usage overloading or dodgy inflation can stress the tyre and cause those cracks as well. If it’s been in contact with chemicals oils or solvents that’ll do it too.

Keeping the bike in a hot sunny or damp place can make things worse.
 

E-MAD MALC

Active member
Subscriber
Nov 16, 2021
368
197
EAST SUSSEX
Cracked = bin.

Its going to delaminate from the backing, so theres a chance a section will come away in use, leading to tyre failure.
Basically its going to be like getting a puncture, so not really dangerous, but it will spoil your day.

Tyres are cheap enough these days so save on a headache and just get shot of it

Being a pretty new tyre though, maybe send a pic to the manufacturers, and they might just replace it.
I agree with that
Bad production run where the top rubber is delaminating from the carcase layer
 

Swiss Roll

Member
Jul 28, 2021
119
89
Switzerland
Not loosing any pressure and live in NE of Scotland, so that rules out overexposure to sun and the bin! Cleaned sidewalls of both tyres once with cloth that had excess plastic restorer(thrifty I know), but rear tyre fine.
Unless it is the dogs of war you are loosing, it should be "losing any pressure".
 

steve_sordy

Wedding Crasher
Nov 5, 2018
8,680
8,948
Lincolnshire, UK
Unless it is the dogs of war you are loosing, it should be "losing any pressure".
I was told by an English teacher that only those who learned English as a foreign language are picky about spelling errors. So as a native English speaker, my bet is that @Reidy had a simple typo and pressed the "o" twice instead of the once he intended. He is still guilty of course of not checking his work! :eek: Now that is worthy of condemnation! :ROFLMAO:
 

Reidy

Member
Apr 17, 2023
7
3
Moray
Thanks Steve, I thought I was working with a bunch of grown up children and nobody would notice or mention it. Wrong again!
Back on the 2.6 tyre, and on the lookout for a wider wheel on sale.
 

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