Tyre Pressures on kit cars
Discussion
Hello,
I suddenly realised I hadn't checked the tyre pressures on the Marlin for a couple of weeks and they were down at 15psi on one wheel (never good, I gave myself a slap for not checking earlier).
But, em, what are they meant to be? I know on normal cars they are up in the 30's but on the lighter kit-cars what sort of pressures are people running? As a temporary measure I have them at 25 all round, is this too low?
Many thanks.
I suddenly realised I hadn't checked the tyre pressures on the Marlin for a couple of weeks and they were down at 15psi on one wheel (never good, I gave myself a slap for not checking earlier).
But, em, what are they meant to be? I know on normal cars they are up in the 30's but on the lighter kit-cars what sort of pressures are people running? As a temporary measure I have them at 25 all round, is this too low?
Many thanks.
I can't really find any other cars tho, I know they exist, but in the short term I can't find any 
I think I'll leave them at 25 as it seems to ride fine & the weight distribution will be fairly even I reckon (engine over the front, 80kg bloke on the back).
Cheers, thats elivated that worry! Now onto the carbs.
I think I'll leave them at 25 as it seems to ride fine & the weight distribution will be fairly even I reckon (engine over the front, 80kg bloke on the back).
Cheers, thats elivated that worry! Now onto the carbs.
Emmm! Tyre pressures on kits? It would certainly confuse the BIB
. For comfort
, one needs the pressure set low, whilst for performance (and economy) they need to be set high. Somewhere in the middle is where they need to be. The Pilgrim Sumo Mk1 operated very well on the road with 16psi front and 18psi rear. For driving with attitude on track I’d pump them up to 30psi.
If your tyres complain,
they’re telling you they need more air. What I’m saying is that if they squeal
on cornering, they need to be pumped up. On the other hand you don’t want them too hard. My suggestion is that you start at around 24psi and gradually let them down until you hear them telling you that you’ve gone too far. Sounds silly
but listening to them 
works. Den
Pressures can also depend on the size of tyres you're using. Obviously bigger tyres have more air in them so can need less pressure than smaller tyres on the same car.
As Den says, start them at 25psi and gradually drop them (pardon the expression!) until it seems right.
Another rough start point guide with higher profile radials (say 60 series and over) is pump them up and then let air out until the sidewall just develops a small bulge.
That's what I ended up doing with my Mk1 Sumo (Hi Den!) when 25psi seemed far too hard.
As Den says, start them at 25psi and gradually drop them (pardon the expression!) until it seems right.
Another rough start point guide with higher profile radials (say 60 series and over) is pump them up and then let air out until the sidewall just develops a small bulge.
That's what I ended up doing with my Mk1 Sumo (Hi Den!) when 25psi seemed far too hard.
kitcarman said:
:
The Pilgrim Sumo Mk1 operated very well on the road with 16psi front and 18psi rear. For driving with attitude on track I’d pump them up to 30psi.
Den
I though (and was always told) that when going on a track your tyres get more heat.
More heat in the tyre means the air in the tyre is hotter and hot air expands, giving you more pressure.
Therfore you let some pressure out of your tyres when on a track.
That was for bikes, but aren't cars the same???????
[quote=kitcarman. My suggestion is that you start at around 24psi and gradually let them down until you hear them telling you that you’ve gone too far.
Sounds silly but listening to them works.
Den
[/quote]
Well Prince Charles listens to plants, so it's not THAT silly 
>> Edited by Wacky Racer on Friday 31st October 20:52
Sounds silly
but listening to them works. Den
[/quote]
Well Prince Charles
listens to plants, so it's not THAT silly >> Edited by Wacky Racer on Friday 31st October 20:52
Ex biker, and Den.
Correct, on all counts, Hot tyres increase pressure and therefore can overpressure what ever settings you have, but, most people increase tyre pressures when going on track by 10%; this is normally to stiffen the tyre and stop it moving around under you...less tyre squirm can, on some tyres (particularly those with tall side walls) therefore give more grip. Less tyre squirm will save tyre wear, but as the tyres are not squirming under you , they will either grip or not (testing your reactions)...it could there for be considered that reducing the pressure incresses the grip.
And that concludes my example of how to sit on a fence and be non comittal. As for the marlin in question, what is the model and what size wheel / tyre are you running.
Correct, on all counts, Hot tyres increase pressure and therefore can overpressure what ever settings you have, but, most people increase tyre pressures when going on track by 10%; this is normally to stiffen the tyre and stop it moving around under you...less tyre squirm can, on some tyres (particularly those with tall side walls) therefore give more grip. Less tyre squirm will save tyre wear, but as the tyres are not squirming under you , they will either grip or not (testing your reactions)...it could there for be considered that reducing the pressure incresses the grip.
And that concludes my example of how to sit on a fence and be non comittal. As for the marlin in question, what is the model and what size wheel / tyre are you running.
I have a vague recollection from the days when TVRs wore Bridgestones that Bridgestone wouldn't endorse running the tyres at any less than 20 psi - even though the cars felt good at very low pressures. They were worried about them pulling off the rims enough to deflate. If Marlin can't tell you, all I can suggest (over a period of several thousand miles) is to see whether the tyres wear their centres out first (too much pressure) or both their edges (too little). The trouble is that many cars (particularly kit cars) wear one or other edge of their tyres no matter what.
wow, I didn't expect such a large response to be honest!
I've got them at 25psi now, and it feels good at that (the backs were down really low and didn't feel good at all), I'll leave them at that for the minute (I was really just checking with yourselves that I hadn't done something drastically wrong) and check the tyre wear.
Thanks for all the tips, I'll a check on the tyres and stuff now!
I've got them at 25psi now, and it feels good at that (the backs were down really low and didn't feel good at all), I'll leave them at that for the minute (I was really just checking with yourselves that I hadn't done something drastically wrong) and check the tyre wear.
Thanks for all the tips, I'll a check on the tyres and stuff now!
I run 17psi on my Birkin which is about 560kg.
We run tyres on se7ens at 17 to generate heat during road use in order to give a good level of grip. I run the same pressure on track but we are only doing 4 or 5 laps at a time. In the summer the tyres were beginning to overheat on the track htough, producing nice marbles.......These are conti sport contacts, the new car is going to have Yoko A048R`s.
Simon
We run tyres on se7ens at 17 to generate heat during road use in order to give a good level of grip. I run the same pressure on track but we are only doing 4 or 5 laps at a time. In the summer the tyres were beginning to overheat on the track htough, producing nice marbles.......These are conti sport contacts, the new car is going to have Yoko A048R`s.
Simon
The ideal way of checking for the correct pressure would be to use a temperature guage across the tyre tread. Preferably an infrared type as they are quicker to use.
Check one axle at a time.
Check the tyre in the centre and both edges.
When the temp is balanced across the full width you are running the correct pressure.
If edges are hotter then pressure is too low. If centre is hotter then pressure is too high.
If you know someone into motorsports they will likely have the IR temp guage.
Check one axle at a time.
Check the tyre in the centre and both edges.
When the temp is balanced across the full width you are running the correct pressure.
If edges are hotter then pressure is too low. If centre is hotter then pressure is too high.
If you know someone into motorsports they will likely have the IR temp guage.
[quote=kitcarman
If your tyres complain, they’re telling you they need more air.
What I’m saying is that if they squeal on cornering, they need to be pumped up. On the other hand you don’t want them too hard. My suggestion is that you start at around 24psi and gradually let them down until you hear them telling you that you’ve gone too far.
[/quote]
I set my Ultima's at between 17-19psi (more at front than rear).
However I recon this must be too low as when I corner with my pedal to the metal the 315 rears squeel like a banshi
If your tyres complain,
they’re telling you they need more air. What I’m saying is that if they squeal
on cornering, they need to be pumped up. On the other hand you don’t want them too hard. My suggestion is that you start at around 24psi and gradually let them down until you hear them telling you that you’ve gone too far. [/quote]
I set my Ultima's at between 17-19psi (more at front than rear).
However I recon this must be too low as when I corner with my pedal to the metal the 315 rears squeel like a banshi
andycanam said:
If your tyres complain,
I set my Ultima's at between 17-19psi (more at front than rear).
However I recon this must be too low as when I corner with my pedal to the metal the 315 rears squeel like a banshi
Remove 4 spark plugs and then try to make the beggers squeel. Next patient please!!!! Den
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