Yet another Gozza question...this time it's tyres

[Gozza2]

Morning all

I'm researching replacing the tyres on the caravan and noticed something odd - in the owners manual it says the tyres should be 175 R14 (plus load and speed numbers that aren't part of this question!).

There's no profile number, collected wisdom appears to be that this means I should treat it as if it was 175/80 R14 - is this correct?

The second thing is that the tyres currently fitted are 165 R14 - I had these fitted a while ago, lets say 5 years, but they will have been direct replacements for what was there before, from when I bought the 'van. I still have one of the originals on the spare wheel and it is indeed a 165.

I've not noticed any problems with towing, but (other than warranty issues) what would be the potential problems with using a 165 when a 175 was specified?

I didn't buy the van from new, so I've no way of knowing what rubber was on the van when it left the factory, although given the age of the van when I bought it, I suspect I got the original tyres.

My quandary is, should I replace with the same as I currently have, which has given me years of trouble free towing, or with what the manufacturer specified? Or does it not matter? I know that under most circumstances the answer is obvious, it's follow the manufacturer specification...but if my guess is right and that the 165s are what the factory fitted, should I continue to follow what they did?

 

[otherclive]

Morning all

I'm researching replacing the tyres on the caravan and noticed something odd - in the owners manual it says the tyres should be 175 R14 (plus load and speed numbers that aren't part of this question!).

There's no profile number, collected wisdom appears to be that this means I should treat it as if it was 175/80 R14 - is this correct?

The second thing is that the tyres currently fitted are 165 R14 - I had these fitted a while ago, lets say 5 years, but they will have been direct replacements for what was there before, from when I bought the 'van. I still have one of the originals on the spare wheel and it is indeed a 165.

I've not noticed any problems with towing, but (other than warranty issues) what would be the potential problems with using a 165 when a 175 was specified?

I didn't buy the van from new, so I've no way of knowing what rubber was on the van when it left the factory, although given the age of the van when I bought it, I suspect I got the original tyres.

My quandary is, should I replace with the same as I currently have, which has given me years of trouble free towing, or with what the manufacturer specified? Or does it not matter? I know that under most circumstances the answer is obvious, it's follow the manufacturer specification...but if my guess is right and that the 165s are what the factory fitted, should I continue to follow what they did?

Your tyres at 80 ratio are probably C light commercial tyres which are preferable. Strange that the maker fitted narrower tyres than specified. However when I upgraded payload on a van I went the other way narrower to wider which with the 80 aspect ratio meant I lost a bit of wheel arch clearance. If the 165 carry the correct Load Index and the speed rating is okay then I would stay with the 165.

 

[RogerL]

You're right that 80% profile is assumed if not part of the tyre size

If the Load Index is high enough for your caravan's MTPLM +10% margin, then you can stay with the present size - Speed Index is effectively irrelevant since no-one makes tyres with such a low speed index to be a problem for caravans - of course the difference between 175R14 and 165R14 is that the ground clearance will be 8mm less on the 165R14, not a lot but might cause any fitted mover to ground on bumps.

 

[otherclive]

You're right that 80% profile is assumed if not part of the tyre size

If the Load Index is high enough for your caravan's MTPLM +10% margin, then you can stay with the present size - Speed Index is effectively irrelevant since no-one makes tyres with such a low speed index to be a problem for caravans - of course the difference between 175R14 and 165R14 is that the ground clearance will be 8mm less on the 165R14, not a lot but might cause any fitted mover to ground on bumps.

The loss of ground clearance is very small when you do the calcs and this doesn’t include for tyre flattening under loading.

 

[Gozza2]

Thanks everyone for the guidance - I think I'll go with the 175s, as there's a better selection of those with a 99 load rating.