Pot holes and tyre pressure

[T3rminator]

What do people find best to protect rims from pot holes in terms of tyre pressure ?

Using factory recommended pressure as the starting point, will bumping up the pressure help protect rims, and is there a point where too high a pressure (say +8 psi) will increase likelihood of causing damage?

Have read that if you see a pot hole, and its too late to avoid, then the best thing to do is to drive straight over it at speed, hitting it with the full face of the tyre. Does that work? Sounds counter intuitive.

I do have a very small buckle on the outside on one of my front rims, from swerving and hitting a pot hole right on the edge. Its on the outside face, so hasn't caused any balancing issues, fortunately. Will probably avoid regional roads for the next few weeks.

[ford71V8]

One of my biggest pet peeves.
Even moreso when using the car with 20" rims.
Best solution obviously is to not hit them. They are everywhere, from behind you might look like you've had 15 pints but your rims and rubber survive.

When its too late I see the thinking behind hitting them square on, but yeah any hit has potential for damage. I see a fresh deep one just around the corner from home, just the right distance from centre of road for it to be in line with everybody's front right

[arm79]

I run the tires on all our cars at 38 to 40 psi. 38 on the 17's and 40 on the FPV with 19's. But they still get buckles on the inner edge. In Dad's case it doesn't help that he seemingly aims for potholes and gutters.

I'd have to send the rims on the FPV away for straightening every 12 to 18 months even when running 40psi. Nothing seemed to properly save them.

[T3rminator]

I used to run 38psi on my 18s, but it got a bit annoying on suburban streets with all the tram tracks, man holes, speed humps etc. Dropped it to 35 and its so much more comfortable.

Have hit a fair few pot holes in recent months, mostly out in the country roads doing 100 to 110kmh. So far so good in that there has been no damage (that I can see!!). The outer buckle I got was in an 80kmh zone, if I recall correctly, I hit the brakes lightly and swerved, apparently the two things you shouldn't do. From memory, I was running 38 psi at the time.

Originally Posted by arm79

I'd have to send the rims on the FPV away for straightening every 12 to 18 months even when running 40psi. Nothing seemed to properly save them.

How much does it cost to do that? The local bob jane told me that factory rims are weaker than the reputable aftermarket ones. I believe them, because the 17 inch XR rims that came with the car had inner buckles all over the place and on all 4 wheels.

[arm79]

Yeah, the B-series factory rims overall seemed pretty weak. The inside of Dad's rims look hexagonal shape. POS Ghia isn't too pretty either.

I think most of my problem with the FPV was the driveway at my old work. It was an old site in Laverton and had one of hose stepped gutter driveways and the step was bigger than normal. If I went over the driveway at the wrong angle it would damage the rim, so I worked out if I went a particular way the chance for damage dropped. My driveway at home was the same, but the step wasn't as tall.

I always got them repaired at Neway Wheels in Preston. It's been a long time but I think it was around $70 to have the inner edge fixed. Was $30 to $40 more to fix up any chips or gutter rash and repaint the lip. They always did a great job, but cant speak for them these days.

The worst part was I could only get 1 wheel done at a time, or if I was very lucky occasionally 2. So I'd have to drop a wheel off, go back a couple of days later and swap out a rim and go back in a few days. Took a week or 2 to get them all done.

[mad2]

so what ya sayin is ..... i should stick with the 16" wheels & only use the 17" when going to a 'local' show

[GO FURTHER]

On the subject of pothole damage to rims...

I have often wondered if wheels with a greater number of "spokes" than a wheel designed with less spokes (such as the stock Mustang GT "20 spoke", versus say a 5 spoke wheel), helps lessen the chance of buckling the rim at the same impact speed?

One would imagine that the more spokes radiating from the centre to the circumference of the wheel would help strengthen the wheel and spread the impact load over more structural points... Maybe or maybe not?

Higher tyre pressures, while giving a much harsher ride and greater transmitted impact shock to the cabin when hitting a pot hole, I think would definitely help protect the wheels to a much greater extent.

[T3rminator]

Originally Posted by GO FURTHER

On the subject of pothole damage to rims...

I have often wondered if wheels with a greater number of "spokes" than a wheel designed with less spokes (such as the stock Mustang GT "20 spoke", versus say a 5 spoke wheel), helps lessen the chance of buckling the rim at the same impact speed?

One would imagine that the more spokes radiating from the centre to the circumference of the wheel would help strengthen the wheel and spread the impact load over more structural points... Maybe or maybe not?

Higher tyre pressures, while giving a much harsher ride and greater transmitted impact shock to the cabin when hitting a pot hole, I think would definitely help protect the wheels to a much greater extent.

I have wondered this. I’m going to say “it depends” from my experience. You can have less spokes, but thicker, covering more circumference, and it will probably protect more than more spokes, spread out thinner. Also the construction and material would have a huge say.

The first set of rims that came with the car were the XR 17s. They have 5 spokes, thick, but had inside buckles everywhere. I changed over to PDW C-Spec2 (relatively cheap rims) 17s, also had 5 spokes but were thinner. Had them for about 5 years and not one dint, absolutely perfect. My current rims (procast, same mob as PDW I think?) have 9 spokes, thinly spread out, and already has a small outside buckle. Its 18s though, with less tyre section width, and the dint was made from hitting one mutha of a pot hole.

[arm79]

Originally Posted by GO FURTHER

I have often wondered if wheels with a greater number of "spokes" than a wheel designed with less spokes (such as the stock Mustang GT "20 spoke", versus say a 5 spoke wheel), helps lessen the chance of buckling the rim at the same impact speed?

My experience with buckled rims has been that the buckles only occur on the inside of the rim, never had an issue on the outside. Not unless you run the thing over a gutter of course.

And from there I think it comes down to offset and the strength of the rim.

I ran genuine EL GT rims on my EL. They were a bloody heavy 17 x 8.5" rim. Rim and tyre they weighed neatly 1/3 more than the 19 x 8.5" on my FPV.

The offset on the EL rims are +6, so you can say the hub face is near on the centreline and the spokes attach to the inside of the rim directly below and radiate to the outside, so much of the rim was supported. A/B/F series is +36 so the face is further outside and the spokes don't support as much of the centre.

In regards to factory B-series stuff, I think it was just cheap crap Ford was installing. The AU rims have the same offset but I don't remember any complaints about buckling like the B-series, so its possible to offer a decent rim if they wanted. And dont forget the B-series coincided with Ford taking away wheel production from ROH and sending it overseas. Wheels were no longer being made at an Aussie company by Aussie designers for Aussie conditions. They were just as cheap as possible to conform.

POS Ghia has very thick and chunky 9 spoke alloys, but the rim still has buckles on the inside.

I remember back in the day the GM of the company I worked for bought a new 5 series. One of the original weird looking ones with run flat tires. He lived past Geelong, so drove Geelong to Laverton every day down at that stage a newly finished freeway.

A few months in he had a buckled rim, they replaced it under warranty. Few months later another rim was buckled. They said "it has to be you, you've already done one. You have to pay for a new one". He argued freeway driving doesn't do that, but gave in anyways.

Few months later another buckle. When he looked under the car he noticed the inner edge and bead area of the new rim was redesigned. Far thicker and stronger. He went to a BMW dealership and looked under the new cars there and sure enough, they all had redesigned rims.

Turns out BMW was getting stung with warranty claims on rims. The super hard sidewalls on the run flats were transferring road irregularities straight to the bead of the rim and it wasn't strong enough to resist so it buckled. Just on normal Aussie roads. BMW responded by creating this revised Australian spec wheel that solved the problem and quietly fitted them to all new vehicles, but were screwing over existing owners.

The GM threatened them with a fit for purpose suit at small claims and BMW caved and replaced the remaining 3 wheels with revised versions and refunded the purchase of the second buckle. He never complained about wheel problems again after that.