C250 CDI W204, Correct tyres sizes?

[Paul297]

Hi everyone,

Walked out to a flat rear tyres this morning. Had a look round the tread but no sign of any nails or anything.

Been looking at some quotes for tyres but unsure on whether I've got the right size tyres on my car.

On the front I've got 225/45/17 and on the rear 245/40/17.

Is it right to have 45 profile on the front and 40 on the rear?

Also, is it worth trying to get the tyre repaired, or is it better to get a new one? The told me to check tyre pressures on Friday but they all seemed fine. So obviously a slow puncture.

Thanks

Paul

 

[robin.large]

The wheel and tyre sizes are on the vehicle info stamp, either on door pillar or inside fuel flap.
A slow puncture on two wheels is unusual, as would twin punctures.
Depends when you last saw them pumped up?

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[Blobcat]

The profile is a percentage of width, so as your rears are wider than the fronts then to maintain the overall diameter the profile needs to be less.

I'd look to repair if sufficient tread left and it's in a place that can be repaired

I'd also look for cracked alloys as they are very common unfortunately - you don't "straddle" speed bumps do you?

 

[Paul297]

The profile is a percentage of width, so as your rears are wider than the fronts then to maintain the overall diameter the profile needs to be less.

I'd look to repair if sufficient tread left and it's in a place that can be repaired

I'd also look for cracked alloys as they are very common unfortunately - you don't "straddle" speed bumps do you?

Ah I didn't know about the percentage, thanks. Makes sense.

How do you mean straddle? Reckon I should get the wheel off and have a look for a crack on the inside rim?

The wheel and tyre sizes are on the vehicle info stamp, either on door pillar or inside fuel flap.
A slow puncture on two wheels is unusual, as would twin punctures.
Depends when you last saw them pumped up?

Sent from my ONEPLUS A5010 using Tapatalk

The tyre was fine on Thursday/Friday and seemingly all this week, but was visibly flat come this morning.

Thanks for the replies guys.

 

[Blobcat]

Ah I didn't know about the percentage, thanks. Makes sense.

How do you mean straddle? Reckon I should get the wheel off and have a look for a crack on the inside rim?


The tyre was fine on Thursday/Friday and seemingly all this week, but was visibly flat come this morning.

Thanks for the replies guys.

Drive over the speed bumps (the ones like a cushion) with one wheel on either side

This puts tremendous strain on the unsupported inner edge of the wheel and tyre - leading to cracks and knackered tyres.

 

[robin.large]

Someone once told me that at 60mph plus the suspension would work as designed and absorb the bump.
I tried this with s VW Combi in Egypt and ended up in a canal. So I'm not a fan!
As others note straddling speed bumps stresses the wheel and the suspension in entirely the wrong way, depending if you can fit the speed bump between the wheels.

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[Paul297]

Drive over the speed bumps (the ones like a cushion) with one wheel on either side

This puts tremendous strain on the unsupported inner edge of the wheel and tyre - leading to cracks and knackered tyres.

Ah okay, I get you. I do that sometimes, if there's oncoming traffic for instance.

I've had a look on the inside rim (got the Mrs to roll it forward while I looked underneath) and I can't see any obvious cracks.

Pumped it back up, been to the shop and back (25 mins round trip) and don't think the pressure has changed. Can't imagine it'd lose that much pressure though (it'd gone down to about 12psi) if there wasn't a leak somewhere...

 

[mattkh]

(got the Mrs to roll it forward while I looked underneath)

DONT do that again. Safest to use an axle stand.
As regards the pressure loss, it could be the valve. Easy to check with a soapy bubble.

 

[Srdl]

Any decent tyre place will be happy to remove the wheel and put it in a water bath to check for the leak. That is the best way to identify whether it’s puncture, valve or cracked alloy. I’ve had repairs done in the past (like @Blobcat says) * - some years ago but only £20 iirc. The likes of Kwik Fit or Halfords might try to sell you a new tyre (or set) but I think it was ATS I used last time and they were very helpful and did the repair without any issues.

* normally fine in the flat of the tread but side wall or near the edge, where there’s more flex, can be a problem.