Club 80-90 Forums

Have been told that bby putting larger tyres on the rear I would do less revs for the same speed.

If this is the case then what would be the ideal size. Currently have 205/55 R16 91w

My van isn't lowered so the reis plenty of room in the arches.

centro wrote:Have been told that bby putting larger tyres on the rear I would do less revs for the same speed.

If this is the case then what would be the ideal size. Currently have 205/55 R16 91w

My van isn't lowered so the reis plenty of room in the arches.

Those tyres are too small anyway!

by 22mm or 3.36%

putting overly large tyres on is futile without power.
increasing the ratio will just mean you'll be into the box to change up earlier, without extra power
IMHO

This is discussed over and over again by T4 and 5 owners who are known to occasionally put bigger wheels on. Which is occasionally followed by a remap because performance usually goes to pot! I am yet to prove this is then followed by problems stripping drive shaft ends but havnt tried that hard

It does drop the cruising revs at motorway speed. But it throws speedo out and therefore throws out the mileage. conclusion, when buying a 4 or 5 if it has bigger wheels - don't believe the mileage - and if its a T5 with 22" squeezed in, ask if they still have the steelies

I have 205/80s on mine. I can feel the sightly taller gearing, especially at cruising speed where it feels a lot more relaxed. I have no problem with over gearing (but bear in mind ours is a lightly loaded Tin-Top camper). It handles fine and if anything the steering is lighter then before. Plus I like the look of them, they fill the arches nicely



Do all 4 though, not just the rears


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centro wrote:Have been told that bby putting larger tyres on the rear I would do less revs for the same speed.

If this is the case then what would be the ideal size. Currently have 205/55 R16 91w

As Kev said...those are too small to start with and not load rated either!

Just by changing them all to 215/60/16's you will instantly notice the difference driving wise....plus they're load rated as well.

Oops, I missed the 16" bit when I replied

Just do the back then the speedo stays the same.

kit wrote:Just do the back then the speedo stays the same.

They're still the wrong size and not load rated and the speedo will still read wrong as they're too small.............

195x70x15 all round. Transformed mine. Gearing feels right, cruises lovely and speedo bang on. The stock 14" wheels and tyres always felt like I was driving on rollerskate wheels and the speedo was miles off!

CovKid wrote:195x70x15 all round. Transformed mine. Gearing feels right, cruises lovely and speedo bang on. The stock 14" wheels and tyres always felt like I was driving on rollerskate wheels and the speedo was miles off!

centro wrote:Currently have 205/55 R16 91w

16" wheels.....

kit wrote:Just do the back then the speedo stays the same.

By my reckoning - based on the sat nav readings before/after fitting my bigger tyres….. the speedo over read by 10% with standard 185's …..so now with the bigger tyres (215/80/14's) its now accurate…

Best

Matt - brighton

Before you jump straight into size changes, do check the regulations. Local tyre place close to me said there are now tighter rules on differences between front and back wheels/tyres. And no need for caps - with 55s on 16" wheels, it won't be vastly different in rolling circumference to 15 X 70s although the price difference between low profile and plain big tyres will be marked. Many low profile tyres are not 8ply either so that may limit what you can do. Anytthing less than 8-ply and they won't comply with the laden weight. You'll also get punctures more easily.

As said, theres not much point unless you have the power behind it and even then, any gains would be almost insignificant.

I used to run 255/50 17 on the rear of mine, it was great on the motorway and would cruise all day at 80MPH. But when around town I found myself dropping it into first, even with a 5 speed box. I've recently had them changed with something slightly smaller and it drives a lot better, even though I've had to slow down a little.

It's worth checking the actual change in diameter using something like this before making a purchase:-

http://www.etyres.co.uk/tyre-size-calculator" onclick="window.open(this.href);return false;

A standard T3 tyre is 185 /80 / 14 = 652 mm diameter as a starting point (R = 80% profile)

discipleofsketch wrote:It's worth checking the actual change in diameter using something like this before making a purchase:-

http://www.etyres.co.uk/tyre-size-calculator" onclick="window.open(this.href);return false;

A standard T3 tyre is 185 /80 / 14 = 652 mm diameter as a starting point (R = 80% profile)

Cool, so my "upping" from 205/70/14 to 205/80/14 results in an increase in diameter of 6.4%, and an increase in circumference of 129mm.

Just need to figure out the maths now to equate that to work out how much further I travel as a percentage Is it the 6.4% increase in diameter times π to get the percent increase in circumference ? Nah, can't be that because that gives 20% increase in rolling circumference (that would mean that before, if I drove 100 miles, I would now be doing 120 miles

Anyone ?

p.s. = I know that non of this can be easily translated into any meaningful MPG figures by the way.