Joined: 20 Oct 2008 Posts: 23 Location: Canvey Island, Essex, UK
Posted: Tue Jul 09, 2019 3:21 pm Post subject:
Nicky wrote:
I am running 165/80/15 on a split. I have seen a set of 3.5”x16”. Can anyone tell me what the 3.5” is compared to the 165? and if they will bolt straight on the bus? Am hoping to use the same tyre depth to make the gearing a little better. Any input would be greatly received.
1 inch = 25·4 mm so 3·5 inches = 89·9 mm, which is just slightly more than HALF of 165 mm! Those tyres are probably off something like a motorcycle, a Citroen Deux Chevaux or something similar, so even if you could somehow fit them on your alternative 16 inch wheels the minimal load rating would be wholly inadequate; even for an unladen split-screen VW Type 2!
If you want to use 16 inch wheels, something like 195/65 R16C tyres would be the most appropriate, but you would need custom-made wheels with the 205 mm PCD or 16 inch wheels from a very-early-model split-screen VW Type 2. _________________ Nigel A. Skeet
Ah. I had an idea this maybe the case but was unsure. Thanku for the info. If I went for a 16” rim with a smaller tyre depth like a 65 I would be defeating the object as I currently have 80 tyre depth on 15”rim. Looks like it’s a no go then!! Was hoping I could buy 16” rim and still use the 80 tyre depth
Joined: 20 Oct 2008 Posts: 23 Location: Canvey Island, Essex, UK
Posted: Wed Jul 10, 2019 3:32 pm Post subject:
Nicky wrote:
Ah. I had an idea this maybe the case but was unsure. Thanku for the info. If I went for a 16” rim with a smaller tyre depth like a 65 I would be defeating the object as I currently have 80 tyre depth on 15”rim. Looks like it’s a no go then!! Was hoping I could buy 16” rim and still use the 80 tyre depth
Why do you specifically want to use an 80-Series tyre? What is the object as you perceive it?
The external circumference, diameter & radius of the tyre tread, depends upon a combination of three factors, which are (a) wheel-rim diameter, (b) tyre section-width, and (c) tyre aspect ratio.
A 165/80 R15 tyre has approximately the same external circumference as a 185/80 R14 tyre, 195/70 R15 tyre and 195/65 R16 tyre. The external circumference of a 215/65 R16 tyre is about 5½ percent larger than that of a 165/80 R15 tyre or 185/80 R14 tyre, etc. _________________ Nigel A. Skeet
Hi Nigel.
Thanku for your reply. This is my theory. I currently have 165/80/15. If I use a bigger rim size ie. 16” x 80 (not sure on the width yet). The overall circumference would be greater so top speed would be increased at the same revs and also gearing would be a little longer. Am I right in thinking this or am I totally talking rubbish?? If my theory is correct would it even be noticeable??
Your feedback would be greatly received. Regards.Nicky
Joined: 20 Oct 2008 Posts: 23 Location: Canvey Island, Essex, UK
Posted: Thu Jul 11, 2019 3:02 pm Post subject:
Nicky wrote:
Hi Nigel.
Thanku for your reply. This is my theory. I currently have 165/80/15. If I use a bigger rim size ie. 16” x 80 (not sure on the width yet). The overall circumference would be greater so top speed would be increased at the same revs and also gearing would be a little longer. Am I right in thinking this or am I totally talking rubbish?? If my theory is correct would it even be noticeable??
Your feedback would be greatly received. Regards.Nicky
If you use a tyre of larger external circumference, then for a given true road speed, your engine will be revving slower in any given gear. Note that at that same true road speed, your speedometer will give a lower reading.
Given that you have a pre-1968, split-screen VW Type 2, your wheel PCD will be 205 mm (which is an uncommon size), so alternative wheel choice will be limited. I believe there are some EMPI after-market 17 inch wheels, with 205 mm PCD, but I don't know of any 16 inch wheels with this PCD, apart from the very-early-model split-screen VW Type 2.
Changing the tyre external circumference, alters the vehicle's overall effective engine gearing, which is typically expressed in MPH per 1000 engine-rpm.
Increasing or decreasing the tyre external circumference might decrease or increase your vehicle's maximum attainable true road speed, dependent upon the extent of over-gearing, under-gearing or optimal-gearing for the engine, before and after tyre change. Increasing the tyre external circumference is very likely to decrease your hill-climbing ability and acceleration capability in any given gear.
If you are running either a factory-standard 1200 cc or 1500 cc engine with its matching transaxle, using larger-circumference tyres might be inadvisable!
From the tyre specifications, one can predict the tyres' external circumferences and hence the effect on overall effective engine gearing and speedometer & odometer calibration.
Keep in mind that the speedometer may read up to 10% more than the true road speed but must not read less. It is possible to have speedometers recalibrated.
Nicky wrote:
Am not quite sure what tyre aspect ratio is!! Is say 80 the depth of the tyre and 165 the height ie the circumference of the tyre
A tyre's aspect ratio relates to the sidewall-height as a percentage of the section-width. Your 165/80 R15 tyre has a nominal section-width of 165 mm (actual section-width is dependent upon wheel-rim width), so the sidewall-height is 80% of 165 mm.
Unless your current 165/80 R15 tyres are commercial-van tyres (i.e. 165/80 R15C) then they are unlikely to have an adequate load rating for your vehicle. _________________ Nigel A. Skeet
Last edited by naskeet on Fri Jul 12, 2019 3:30 pm; edited 1 time in total
Joined: 20 Oct 2008 Posts: 23 Location: Canvey Island, Essex, UK
Posted: Fri Jul 12, 2019 3:29 pm Post subject:
Nicky wrote:
Thanku for your sound advice. I shall look into the load rating.
I do not know what the front & rear axles' maximum load ratings are for a pre-1968 split-screen VW Type 2, but for my 1973 VW "1600" Type 2 Kombi based campervan, they are 1010 kg & 1300 kg respectively, so to avoid any problems with the law or voiding the motor-insurance policy, I need front & rear tyres with absolute-minimum load ratings of 505 kg & 650 kg respectively. _________________ Nigel A. Skeet
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