buying 18'' alloys - best tyre size - advice please!

madmile · Post by **madmile** » Mon Feb 12, 2007 8:15 pm

If you go bigger in diameter than standard you will fill the arches a bit, but without lowering you will also end up with a slightly taller van. I think a slightly larger looking wheel / tyre does suit the bongo. I have one with 215/17/55. It is not lowered and I do think it looks better than standard. Also 98 rated tyres quite easy to get.
However,i would have to say I think the best ride still comes with standard rims / tyres- and no insurance hassles.

steveyboy · Post by **steveyboy** » Mon Feb 12, 2007 8:26 pm

Hiya Scott & Sophie,just been through this myself last week i ended up with 225-45-18 on the front and 245-40-18 on the rear it changed the motor totaly for the best.Dont forget your loading

bigdaddycain · Post by **bigdaddycain** » Mon Feb 12, 2007 10:45 pm

I think, if i recall correctly that the overall diameter of the bigger wheel tyre combo was about an inch-inch and a half bigger all round than my old fifteens. the 18"s must be bigger to alter my speedo readings.

bournemouthken · Post by **bournemouthken** » Fri Feb 16, 2007 11:25 pm

[quote="bigdaddycain"]Hi scott and sophie,
I had 15"( 195/70/15 ) alloys on my bongo when i bought it and the speedo used to overead i.e. actual 65 M.P.H would read 72 M.P.H. on my speedometer.
I have now fitted 18" alloys, shod with 245/40/18 tyres, and now my speedometer is accurate according to my G.P.S. i.e. 65 M.P.H is actually 65M.P.H.

Hi, when travelling at 30mph, I get a big que behind me, I have found that my speedo which has a electronic converter fitted is 7 to 10 mph out according to my sat nav, I am now wondering if the speedo chips are built for other vehicles with 18" WHEELS AS STANDARD AS OPPOSED TO THE |Bongo's 15", but are used because they seem to work, after all, if the speedo reads under the actuall MPH then it will pass the import test....what say you...

bigdaddycain · Post by **bigdaddycain** » Sat Feb 17, 2007 5:21 pm

Could well be bournemouthken, my bongo has the speed chip thing fitted also, Although most car manufacturers have a safety margin built in their vehicles to ensure that a higher than actual speed is showing on the speedo, i'm not sure if this is because they are so very concerned that we dont get points on our license, or,to ensure that the same vehicles with different wheel tyre combos can still use the same original speedo equipment to keep the costs down for the manufacturer.

I suspect the manufacturer of the speed chips are doing something similar, i.e. one chip fits most. Keeps their costs down i suppose....

Scott & Gillian · Post by **Scott & Gillian** » Sat Feb 17, 2007 6:39 pm

Checked the speedo on our bongo today against GPS and at 40mph on the dial, we were actually doing a touch over 37mph - this was with 15'' wheels on.
So, am I right in thinking that with 18'' wheels, the speedo should be pretty much right?

francophile1947 · Post by **francophile1947** » Sat Feb 17, 2007 6:45 pm

It depends on what tyres you fit - have a look at http://www.miata.net/garage/tirecalc.html
This will let you see the effect of changing tyre and wheel sizes.

bigdaddycain · Post by **bigdaddycain** » Mon Feb 19, 2007 2:07 am

That was a good site francophile, very informative... and yes scott and sophie, that is the general principle,if you go a few inches bigger, you will catch up on the safety margin in the speedo...

David Edwards · Post by **David Edwards** » Mon Feb 19, 2007 1:43 pm

One thing to remember about fitting alloy wheels, they are softer than normal steel wheels, especially if there is only one rim to them, if you see what I mean, "the washing up bowl with holes effect), this means the inner rim is VERY VERY susceptable to damage and even the smallest of pot holes can cause them to dent or buckle and that it then, knackered for good, I know of one poor chap paid an arm and leg for a set and within six weeks they were useless, dented from bad roads etc that was on a go faster vw golf, remember the bongo is a heavy vehicle so damage would occur easier. Good luck though and happy motoring.
With the speedo, mine too shows faster than the sat nav, I am leaving it alone, very handy where speed cameras are about.

bigdaddycain · Post by **bigdaddycain** » Mon Feb 19, 2007 2:01 pm

That is quite correct david,i too, on one or two occasions have suffered damaged alloys on a couple of occasions over the years, from very big potholes etc. (usually at night,when you cant see em) I think the profile of the tyre has a bearing on the chance of damaging the inner rim. When my wheels have been damaged, it has been with a 35 section tyre, which is very low profile. The lower the profile, the less give the tyre has due to its shallower sidewall. With the bongo, 40 or 45 section tyres should be fine. ( unless you slam into a missing manhole cover or something)

trevd01 · Post by **trevd01** » Mon Feb 19, 2007 2:17 pm

That why I stick with big fat 65 profile 15 inch tyres. My wife has destroyed two 40 profile tyres on her Audi in the last year, on the road leading to our house, which the council say is 'on their list' to resurface this year.

David Edwards · Post by **David Edwards** » Mon Feb 19, 2007 2:36 pm

The lad who trashed his took pictures of the pot hole, as did his pal who was with him, he telephoned and complained to the council who gave him details of the legal section to contact. later that day he returned to the road and found the pot hole and several others filled in already, lucky he had photo evidence and an independent witness, he got his comp from em. Happy motoring.