New wheels

[GowerOsprey]

Hi all

Before I start, I feel I must point out that I'm very reluctant to post this question, as if I get an answer I don't want, it could cost me £250!

My Bongo is in need of at least two new tyres, and realistically, a full set. A good friend of mine has offered me a set of alloys with tyres for £50, with bolts. I have just tried one of them on the rear of my van, and unbelievably they fit perfectly! They are Jap import tyres that he bought incorrectly from eBay about two years ago and have been sitting in his garage ever since.

My query relates to the vital statistics of the wheels and tyres:
I currently have 195/70 R15 92H on the front and 215/65 R15 96H on the back; they were on the van when I bought it last August.
The alloys being offered are all 215/50 R17 91W.

I have read the factsheets and looked at (I can't really say I read them, as I only understood about 60% of what was written!) the previous topics on the forums relating to tyres and their effects of performance, consumption and safety, and I am really unsure as to whether the offered set of alloys and tyres are suitable. Since we use the van extensively for camping, more often than not in muddy fields (!), one area that I would be concerned about on top of those mentioned above, is how changing the wheels would affect grip on grass and mud.

Hope someone is able to help shed some light on my dilemma, many thanks for viewing.

[missfixit70]

91 load rating is too low, this thread may help - http://www.igmaynard.co.uk/bongo/forum/ ... =5&t=51452
The wheels themselves should have a load rating on them.

[GowerOsprey]

Thanks for your swift reply. Can you explain what the consequences of having a too-low load rating would be?

I've just been out to look at the alloy and tyre I was given and got this data from the inside of the wheel; it was by torchlight but I'm 99% sure that this is correct:

17X7 JJ E 396-29 03
A 56
B 48
C 61

The wheel appeared to fit perfectly (and I measured the diameter of the central bore hole of both the current and potential wheels and they were the same) but I see from the thread link given in your post that these do not match those given on the Service Data sheet scanned by your good self.

Could you take pity on a clueless chap and explain what these numbers actually mean, and whether or not it rules out these wheels as suitable?

[missfixit70]

There is no direct data available for the wheels, but the assumption is that the load rating for the wheel (usually marked in kg) should be comparable to the minimum load rating equivalent for the tyre, ie a load rating of 96 on the tyre is a payload of 710kg per tyre, load rating of 91 is 615kg per tyre.
Potential consequences of too low a rating is tyre or wheel failing under laod/braking etc, or insurance voiding your policy if the wheels/tyres are deemed underated, especially if they contribute to an accident.
The factsheet in the members area explains what the tyre ratings are about, or google tyre & ratings, it'll be explained better than I could, & that's all I'd be doing. I am no tyre/wheel expert, just going by the data available & a sense of preservation.

[GowerOsprey]

Thanks again missfixit70.

I'm not sure if you're able to answer the following question, but I'm gonna throw it out to see if you or anyone else has the requisite knowledge....

The tyre data sheet shown on the linked forum thread shows different load ratings for the front and rear tyres, i.e 92 on the front and 96 or 98 for the rear tyres. Using the widely available Load Indices I've made the following calculations:

If L.R. = 92, the load on the front tyres would be (2 x 630Kg) = 1260Kg
If L.R. = 96, the load on the rear tyres would be (2 x 710Kg) = 1420Kg
The sum of these two loads is 2680Kg.

Would it therefore be safe to fit two of the proffered tyres (L.R. = 91) on the front of the van, and replace two of the tyres with ones with a L.R. = 97 or 98? This question is posed based on the following calculations:
Front: L.R. = 91, load = (2 x 615Kg) = 1230Kg
Rear: L.R. = 97, load = (2 x 730Kg) = 1460Kg
Total load = 1230 + 1460 = 2690Kg (this would increase to 2730Kg if I put 98s on the rear; see below).

I have been looking at Rockstone F105 215/55 R17 W (98) tyres from Blackcircles.com, purely for the sake of finding out potential costs. The aspect ratio is lower than for those given on the tyre data sheet, but then the wheel is 17" not 15"; does this matter?

Or have I massively over-simplified the case, and need to be looking at the Mazda recommended load rating for the front of 92 as the minimum that I can replace with?

Apologies if I'm making a mountain out of a molehill here, but if I can save even a small amount of money on a full set of new tyres, it's gotta be worth asking hasn't it?!

P.S. I hope you are able to follow my maths above! The load indices I used were here, right at the bottom of the page: http://www.carbibles.com/tyre_bible.html

[missfixit70]

If you read the link I provided above

Eek! my tyres are rated 93V all round. Although from what I can gather googling this covers a max load of 2600kg which should be 20-25% above vehicle weight. I don't have a camper conversion or a van full of people so hopefully I'm ok
Also just got the van back from garage with autobox serviced and oil pan straightened out. Was £240 a good price anyone?
Cheers,
Martin

Ok, I'm not trying to scaremonger here, but that doesn't leave you much margin for loading the bongo (are you really going to drive around with it empty? - it's very easy to overload a vehicle of that size without realising it) & you're under the recomended tyre ratings in the handbook & on the drivers door plate





As you can see it says that 92S is ok for the front for a 195/70R15, but as soon as you move up to 195/80R15 the recommended rating is 96S.
For the rear you can see that the rating increases to 98S from 96S when you go from a 215/65 to a 215/70.
Personally, as you (& many of us) are fitting non standard wheel sizes, I would prefer to take the maximum value there & make sure all the tyres are above that, rather than the minimum, especially when fitting same size tyres all round.
Also worth checking the age of the tyres, anything above 7 years isn't good.
I would suspect (as has been discussed on here MANY times) that using tyres that could be considered underrated could invalidate your insurance in the event of an accident.
Your tyres are the only thing sticking you to the road, is it worth the risk?
I am no tyre expert, I just like to have a bit of belt & braces safety margin, especially on mine where I often tow a trailer or have a box & bakrak/bike & bikerack.
The tyre pressures on these specs will be a bit low for uk spec modern tyres, apparantly Jap spec tyres were a softer compound.

As for the case for increasing the load rating on the rear axle to compensate for the below recommended rating on the front, I'd think not TBH. Where does all the weight get thrown when you slam on the anchors?
As I said, I am NOT a tyre expert but I would put safety above a potential bargain.

[munroman]

Hi, although I can understand the temptation of having 'almost right' tyres available at an excellent price, if you use under spec tyres anywhere you run the risk of being uninsured if you have an accident, as well as possible prosecution for incorrect tyres.

Ask yourself how much that could be worth and perhaps that puts some perspective on the costs involved.

If your Bongo is a 4wd there is also the issue of the need for front and rear tyres to have similar circumferences.

As Kirsty has said, there is loads of information here on previous threads, including ones where people have destroyed axles by not using the correct tyres.......

[Jaws]

I would not be happy to fit imported (part worn?) tyres to any vehicle if they have been sitting around somewhere for a couple of years. Just my view naturally, but safety comes first.

The alloy rims are probably OK to use but please bite the bullet and get the right (new) tyres fitted.

You need to consider the load rating and rolling diameter. Remember the original specification was for a people carrier rather than a fully loaded camper. I use 215/65 98H on 16" rims all round. There are plenty of other combinations which will work but the load and speed rating of each tyre must at least match the original spec or there may be problems ahead!