Tyres (sorry!)

[GICarey]

Hi all,

Well, picked up the Bongo today! yeay! Covered about 60km thus far, and so far so good, though a few amusing oddities:

* Rear-wiper - fitter so that it wiped the lower half of the door, rather than the rear screen - easily solved
* Rear-foglight - blown bulb (easily replaced)
* Front foglights - Switch incorrectly wired up - now corrected
* Rear screen heater - switch wasnt connected to the connector

Get the feeling someone has been playing with the electrics. still all ok now!

So, onto the reason for this topic.....

Rather than the standard R15 wheels, previous owner has popped on some Nissan Alloys. 16" wheels, and very nice they look too..

However, the tyres on said wheels are 215/60 R16 95 (same on all wheels). Theyre Nexen CP641s. Look quite new.

So, my first question then, is, is this OK? The Bongo is a 4wd so, i think, the fact that they're all identical is good? and the only thing to be concerned about is impact on the speedo? (it seems to under-read by about 5mph - comparing to the GPS)


Draggin myself underneath, and taking a gander at the spare - it's a space saver (think this is normal?). The tyre on there seems to be the original one from Japan, it's an 185/90 D15. So, my second question is, given the tyre & wheel sizes above. Is the overall circumference of the spare going to be significantly different from the main ones? and thus unusable?

Thanks, in advance!

Gav.

[missfixit70]

Bin the spacesaver, useless & dangerous IMO, only good for 80 km at 80km/h. get a full size spare.

[John the sparky]

I run 16's on my bongo, same size alround shouldn't be a problem (seems smaller fronts are for handling rather than anything particularly clever, and as long as all tyres are wearing at same rate, then you should have no probs with transmission windup) but what do I know, mines 2 wheel drive

but 95s aren't up to spec from mazda for rear tyres,

spec'ed as 92s front and 96's rear......

so the fronts are more than adequate.... but the rears are a little under (20kg..... 95's are 690kg load rating and 96's are 710kg)

now I not even going to get involved, but technically they are not up to spec and could be considered contributary in an accident (I think?) or...... it's only 20kg.... so if you don't fully load it, will it matter?

hope this helps

John


(oh....forgot to say, I am in the process of sorting a 16" spare, so will have a full size (15" 215) steel up for grabs in a while, if you can wait a couple of weeks, I could meet you half way somewhere)

[GICarey]

Bin the spacesaver, useless & dangerous IMO, only good for 80 km at 80km/h. get a full size spare.

Will a full size spare fit where the space-saver is? or does it need to find a lodging inside the bongo?

[missfixit70]

Full size spare fits fine, most of us have got them

[GICarey]

Echelente, thanks Kirsty!

will see if i can find one round here (i geuss a 16" hub with same tyre fitted as the alloys is the way to go)

[daveblueozzie]

the spare does not have to be a 16" you can use an ordinary bongo 15"steel wheel ,after all its only a spare, enough to get you home or wherever then you can fix the alloy.

[John the sparky]

yeah, I wouldn't bother too much myself, but scored a matching 16" alloy, and if I fit it, it won't be hanging around in the shed.....

I'd look out for a 15", they seem to get given away periodically, and use that as a full size space saver, if you see what I mean....the problem with the space saver is you have to run at high pressure, and if not up to pressure, it can run the tyre of the rim, particularly when fully loaded (so I was led to believe, anyway) where you shouldn't get this problem with a full size wheel,

there is a tyre calculator....

http://www.miata.net/garage/tirecalc.html

and the difference between a 215/65 15 and a 215/60 16 is negligable


John

[sparkymik]

I was just wondering with going for larger tyres and your speedo will be slower than road speed, you will need to be carefull through these new average speed traps on M-Way works where you average over 50 is taken, you could end up getting busted if you don't concentrate on you speedo reading , which is hard enough to do over a few miles anyway, or am I wrong, as I say just a thought

Sparky

[GICarey]

Thanks Sparky,

I was worried about this too, so did a test on the motorway t'other day, had the misses calling out velocity from TomTom, and commparing to the spedo. It seems the speedo is under-reading by about 5mph (so, at 30mpg on the speedo, i'm really doing 25mph - or is that the speedo over reading - anyway...). Suspect this will. ultimately. lead to my being a slower driver!

As I'd have thought, if i've moved to a bigger overall diameter, i should be reading faster, not slower (more distance covered per turn of the wheel), so either the rim & tyre combo is a smaller diameter than the previous R15s and normal tyres, or the speedo is wholly innacurate anyway!

Anyone have thoughts? When I get home tomorrow, I might try that tyre calculator and compare my actuals (from top if this chain) to standard tyres for a 4WD Bongo and see how they compare!

Cheers,

G.

[John the sparky]

it's because of the aspect ratio

the middle bit of the tyre size...

215 is width (in mm)

65 is the size of the sidewall, it is actually aspect ratio, 65 is 65% of width, so 65% of 215 is 140mm
the 16 is the size of wheel in inches


so the important bit is matching the rolling circumference, and dropping the aspect ratio to compensate for a bigger wheel


I run 225/55 16s with xl99 tyres on mine, which is exactly the same size as the standards, and checked against road angel is spot on for speedo.....but remember your speedo may be running out regardless, and I have a mazda 626 mile speedo fitted, which may also be a factor,

but to be honest, it all sounds about right, I'd run as is and when a couple of tyres wear, put high load rating tyres on the back and worry about changing the sizes, if at all, when they all wear out!

John

[sparkymik]

Hey Gav
if you go to the FAQ section there is an interesting FAQ by a bloke that get 40mpg out of a bongo, he go's to some lengths about tires and sizes and the overall effect on the speed over ground and speed through the sensors, I think if your speedo is slow your speed over ground is high do to your tyre circumference being longer or go here http://www.miata.net/garage/tirecalc.html and this will help, mine has 215/65/15 all round inflated to 40psi all round I read this in the same FAQ as the speedo thing, it's supposed to be a better ride more econical and more stable, I only did this mod yersterday so it's early to say anything on economics but the ride is a lot better, hope any of this helps mate

MiK

[John the sparky]

[GICarey]

HI all,

Thanks for the tyre-calc link. I've also had a look through the Tyre Fact Sheet.

So, comparing stock tyres (215/65 R15) with the ones on my Bongo (215/60 R16), it tells me that the circumference of my new wheel & tyre combo is 0.5 inches out, and that (if my speedo were accurate, which it seems it is not) when it were showing 60mph, i'd actually be doing 60.4mpg.

I think the difference (on my speed), therefore, is negligible, and my innacurate speedo is far worse. As for the strength ratings. You're right, they're 20kgs under-spec, but I think, as I've no conversion, and we rarely carry anything approaching a full load, this is unlikely to be a problem. I'll likely correct it when the existing tyres are worn out.

Have now made myself a note in my log book as to which tyres to have fitted when it comes replacement time!

Gav.

[Chas]

Legally a speedo should show not under read (ie show a speed less than you actual speed) and is permitted to over read by 10%. IME most speedos over read by about 10%

Chas