Moronic questions (from me) about inner tubes/tyres
Discussion
Ok, the DS is the first car I've ever owned that uses inner tubes (due to riveted rims). I have a few questions about them if anyone would care to enlighten a cretin? 
1) Tyre pressures - do I need to make any adjustments? If I want a true 30psi for example do I simply fill the inner tube using (Tesco's) pump to 30psi? The reason for asking this is two fold. a) in my mind there will always be some air between tube and tyre (may be catastrophically wrong about that!) and b) I inflated my front tyres recently to the handbook suggested pressure of 29psi and they felt mighty squashy (by hand.)
2) (related to 1) - The handbook suggests a tyre pressure of 29psi. However, I am not using the same tyre size that this applied to (original tyre size was 185/80/15, I am using a 195/70/15). Should I be putting in a higher/different pressure do you think?
3) If I get a puncture, for example a nail/screw, do I simply replace the inner tube rather than the tyre? I assume there is a bit of common sense here and if it is a big hole then obviously new tyre is needed.
1) Tyre pressures - do I need to make any adjustments? If I want a true 30psi for example do I simply fill the inner tube using (Tesco's) pump to 30psi? The reason for asking this is two fold. a) in my mind there will always be some air between tube and tyre (may be catastrophically wrong about that!) and b) I inflated my front tyres recently to the handbook suggested pressure of 29psi and they felt mighty squashy (by hand.)
2) (related to 1) - The handbook suggests a tyre pressure of 29psi. However, I am not using the same tyre size that this applied to (original tyre size was 185/80/15, I am using a 195/70/15). Should I be putting in a higher/different pressure do you think?
3) If I get a puncture, for example a nail/screw, do I simply replace the inner tube rather than the tyre? I assume there is a bit of common sense here and if it is a big hole then obviously new tyre is needed.
If I want a true 30psi for example do I simply fill the inner tube using (Tesco's) pump to 30psi?
- no, garage tyre pressure gauges tend to be very inaccurate buy a foot pump and a reliable seperate tyre pressure gauge
in my mind there will always be some air between tube and tyre (may be catastrophically wrong about that!)
- er, you're inflating the inner tube and indirctly the tyre - have you never owned a pushbike
I inflated my front tyres recently to the handbook suggested pressure of 29psi and they felt mighty squashy (by hand.) . . . The handbook suggests a tyre pressure of 29psi. However, I am not using the same tyre size that this applied to (original tyre size was 185/80/15, I am using a 195/70/15). Should I be putting in a higher/different pressure do you think?
- you've answered it yourself you're not using the same size (and probably type of) tyre as in the Handbook (full marks for having the Handbook though) with modern tyres you could try increasing the pressures by a couple of psi
If I get a puncture, for example a nail/screw, do I simply replace the inner tube rather than the tyre? I assume there is a bit of common sense here and if it is a big hole then obviously new tyre is needed.
- yes, yes – if you’re going to rally the car though, depending on the type of rally, you might be better with different wheels that don’t need tubes
- no, garage tyre pressure gauges tend to be very inaccurate buy a foot pump and a reliable seperate tyre pressure gauge
in my mind there will always be some air between tube and tyre (may be catastrophically wrong about that!)
- er, you're inflating the inner tube and indirctly the tyre - have you never owned a pushbike
I inflated my front tyres recently to the handbook suggested pressure of 29psi and they felt mighty squashy (by hand.) . . . The handbook suggests a tyre pressure of 29psi. However, I am not using the same tyre size that this applied to (original tyre size was 185/80/15, I am using a 195/70/15). Should I be putting in a higher/different pressure do you think?
- you've answered it yourself you're not using the same size (and probably type of) tyre as in the Handbook (full marks for having the Handbook though) with modern tyres you could try increasing the pressures by a couple of psi
If I get a puncture, for example a nail/screw, do I simply replace the inner tube rather than the tyre? I assume there is a bit of common sense here and if it is a big hole then obviously new tyre is needed.
- yes, yes – if you’re going to rally the car though, depending on the type of rally, you might be better with different wheels that don’t need tubes
Ok, thanks very much for that.
I do have a decent foot pump so I'll pick up a pressure guage tomorrow - cheers. I think running them at 31-32 all round sounds about right to me.
As for wheels, sadly the DS has a rather specific bolt layout and the only off-the-peg alternative are the magnesium wheels off a 70's race spec SM. I've only ever seen one full set sell before at auction; £8000+ tax and buyer's premium. Ouch. I toyed with the idea of buying a set of the newly reissued Wolfrace Slotmags but the car just wouldn't look right on alloys. Plus the steelies can be banged out with a hammer if I stuff it off a Col on the top of the Alps
I have also just spend (an admittedly pleasant) three evenings in the garage painting the 4 spare DS rims I bought specifically for racing so a bit late to backtrack!
Cheers,
Ben
I do have a decent foot pump so I'll pick up a pressure guage tomorrow - cheers. I think running them at 31-32 all round sounds about right to me.
As for wheels, sadly the DS has a rather specific bolt layout and the only off-the-peg alternative are the magnesium wheels off a 70's race spec SM. I've only ever seen one full set sell before at auction; £8000+ tax and buyer's premium. Ouch. I toyed with the idea of buying a set of the newly reissued Wolfrace Slotmags but the car just wouldn't look right on alloys. Plus the steelies can be banged out with a hammer if I stuff it off a Col on the top of the Alps
I have also just spend (an admittedly pleasant) three evenings in the garage painting the 4 spare DS rims I bought specifically for racing so a bit late to backtrack!
Cheers,
Ben
Expatloon said:
Be a bit careful, not many tyres these days are designed to have tubes fitted and the rougher inner surfaces can rub and puncture them.
There should be a little square symbol on a tyre designed for tubes.
Oh cock. I'll have a look.There should be a little square symbol on a tyre designed for tubes.
Edited by Expatloon on Monday 17th October 19:12
A simple way to check if you are running the correct tyre pressure for any non standard tyre size is to use the 4psi rule.
Most tyres are designed to run at around 4psi above the manufacturers cold tyre pressure setting when up to their normal operating temperature.
If you set the cold tyre pressure to the manufacturers setting (in your case 29psi) and then drive the car for approx 20-30 minutes and then check the pressure it should read approx 4psi above the original setting, in which case the manufacturers setting would be the correct one for your new tyres.
If it reads more than 4psi above then the tyre is running hot (under inflated) and you will have to increase the original setting. If it reads under 4psi then it is running cool (over inlflated) and you will need to reduce the original pressure.
This is a fairly basic guide but it will tell you if you are running your tyre within the correct pressure range for your vehicle.
Most tyres are designed to run at around 4psi above the manufacturers cold tyre pressure setting when up to their normal operating temperature.
If you set the cold tyre pressure to the manufacturers setting (in your case 29psi) and then drive the car for approx 20-30 minutes and then check the pressure it should read approx 4psi above the original setting, in which case the manufacturers setting would be the correct one for your new tyres.
If it reads more than 4psi above then the tyre is running hot (under inflated) and you will have to increase the original setting. If it reads under 4psi then it is running cool (over inlflated) and you will need to reduce the original pressure.
This is a fairly basic guide but it will tell you if you are running your tyre within the correct pressure range for your vehicle.
Good one from Expatloon about tubes rubbing I meant to put that but was being called for food, I know it happens because I had it when I had car wheels with tubes (took a long time with my tyres though)
but I didn’t know about the square symbol or bigblock’s 4 psi rule of thumb
a good make accurate tyre pressure gauge but as I have one similar to the one RichB has pictured I’d suggest the type that look like that but that also has a flexible tube to the valve because that one with a fixed rigid neck can be awkward to use on some wheels
but I didn’t know about the square symbol or bigblock’s 4 psi rule of thumb
a good make accurate tyre pressure gauge but as I have one similar to the one RichB has pictured I’d suggest the type that look like that but that also has a flexible tube to the valve because that one with a fixed rigid neck can be awkward to use on some wheels
A bit of experience based advice too that I will emphasise is opinion based and should be taken with a large pinch of salt.
As mentioned other than crap gauges in petrol stations which apply to all cars as far as actual use of the tubed tyre goes it's no different to tubeless.
You mention punctures, you don't need to replace the tyre *use your common sense though* just sort the tube, however don't forget you can actually repair the puncture in the tube (just like a bike) but do get heavy duty patches and make absolutely certain it's a good repair by testing the tube before fitting. You also can get away without removing the tyre from the wheel to pop the tube out usually, make sure the tyre fitter takes care when removing and refitting tyres, they mustn't nick the tube between the bead and rim.
Tyre pressures are a very subjective thing, not all manufacturers got it right from day one, also don't forget many classics were meant to use crossplies or substantially different sizes from standard. I usually start at the standard setting then increase or decrease till I'm happy with the handling, the MGC I'm running at the moment is running at circa 40psi (nearly as high as my old 911) but the handling is now fantastic, it's running modern tyres of a drastically different width and profile to original.
As a disclaimer however it is important you realise with any modification if you make a mistake which results in an accident and it is deemed your modification contributed expect insurance and legal issues. Do not assume because of my advice you can put a badly repaired inner tube back in a tyre, pump it up to 300 psi and blame me when it blows off the rim.
As mentioned other than crap gauges in petrol stations which apply to all cars as far as actual use of the tubed tyre goes it's no different to tubeless.
You mention punctures, you don't need to replace the tyre *use your common sense though* just sort the tube, however don't forget you can actually repair the puncture in the tube (just like a bike) but do get heavy duty patches and make absolutely certain it's a good repair by testing the tube before fitting. You also can get away without removing the tyre from the wheel to pop the tube out usually, make sure the tyre fitter takes care when removing and refitting tyres, they mustn't nick the tube between the bead and rim.
Tyre pressures are a very subjective thing, not all manufacturers got it right from day one, also don't forget many classics were meant to use crossplies or substantially different sizes from standard. I usually start at the standard setting then increase or decrease till I'm happy with the handling, the MGC I'm running at the moment is running at circa 40psi (nearly as high as my old 911) but the handling is now fantastic, it's running modern tyres of a drastically different width and profile to original.
As a disclaimer however it is important you realise with any modification if you make a mistake which results in an accident and it is deemed your modification contributed expect insurance and legal issues. Do not assume because of my advice you can put a badly repaired inner tube back in a tyre, pump it up to 300 psi and blame me when it blows off the rim.
good points again
accurate gauge for use on all tyres, sorry if it seemed as I meant for tube tyres
puncture repair (as per pushbike example was lost by me in my gut filling rush)
tyre pressures can be experimental, and the modern tyres seem to have a range of tolerance, plus the pressures can be balanced to a certain extent with the suspension set up for ride
and of course always best to check your insurance cover before an accident
accurate gauge for use on all tyres, sorry if it seemed as I meant for tube tyres
puncture repair (as per pushbike example was lost by me in my gut filling rush)
tyre pressures can be experimental, and the modern tyres seem to have a range of tolerance, plus the pressures can be balanced to a certain extent with the suspension set up for ride
and of course always best to check your insurance cover before an accident
johnfm said:
So, can you use tyreweld type emergency puncture sprays with an inner tube??
as we had a long thread on this on another forum I can say 'No'plus it says it on the can
ETA: when used on a tyre it's a get you home at 30 mph or less and the tyre will be replaced by the fitter and you'll get charged extra to clean out the wheel
but others have said they've used it and forgotten and continued to use the tyre as normal - but this is NOT recommended as it could be dangerous as the Tyre-weld could mask dangerous problems
Edited by na on Monday 17th October 21:48
RichB said:
johnfm said:
So, can you use tyreweld type emergency puncture sprays with an inner tube??
I've never tried it but I somehow doubt it would work.I think some of the other things you can get such as 'slime' that you fit before the puncture claim to work in tubes though.
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