Safety question: 15" rims fitted instead of 13"

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LeeEnfield
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Safety question: 15" rims fitted instead of 13"

Post by LeeEnfield » 03 Apr 2014 01:01 pm

Hi my 23 year old son has just bought a 1991 1.4 340 5 door which has Rover alloys fitted (tyre is 185 55 R15). Are these larger rims safe? Will they adversely affect steering, heavy braking, normal driving? Or do I need to buy him a set of 13 inch rims from somewhere? I'm just interested in the safety aspects.
Many thanks, worried dad

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Chris_C
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Re: Safety question: 15" rims fitted instead of 13"

Post by Chris_C » 03 Apr 2014 01:52 pm

Hi Lee,

The '91 340 would originally have had a 175/70 r13 wheel fitted, which has a total diameter of 575mm. The new wheels have a diameter of 585mm so 10mm. Overall, its not that much difference and a lot of 300s run them. The 400 series (which has very similar wheel options to the 300, they shared a couple of options) runs 15" on that size of tyre. As overall size is similar, braking and steering will be largely unaffected as long as the offset is correct (which if they are from a fwd car is unlikely)

The only thing to note is the speedo will be under reading by half an mph per 30 (i.e. reading 59 at 60mph road speed). Given how much the standard setup over reads you should be ok.

Only thing I'd say is make sure it is noted on the insurance.
'89(G) 340 GLE B172k
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Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast

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Re: Safety question: 15" rims fitted instead of 13"

Post by classicswede » 03 Apr 2014 02:17 pm

Some of the factory option alloy wheels were 14 inch. I have run on 15 inch wheels with 195/50/15 tyres for a long time and there are no issues. In fact they make the car safer. As the wheels are off a fwd car the offset is probably wrong and the wheels are tucked in to for. Et should be 40 or less. The biggest problem with having the wheels tucked is 1 they are more likely to rub on the body and 2 make the track smaller
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LeeEnfield
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Re: Safety question: 15" rims fitted instead of 13"

Post by LeeEnfield » 03 Apr 2014 02:27 pm

Very helpful, many thanks. I'm confused re FWD and rear wheel drive and how it matters as to where the wheels came from. Let me demonstrate my confusion...are we saying that the wheels themselves are balanced to reflect the FWD geometry (or whatever it's called) so naturally if you take the wheels from such a car then the balance will be out when put on a rwd? Sureley the balance being out thing is the same when you transfer any wheels car to car?
Safety is my main thing. I'm ok with the tyre wearing unevenly IF they do so safely. If they are dangerous though then that's another thing.
Again many thanks to all those with an informed opinion. Lee

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Chris_C
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Re: Safety question: 15" rims fitted instead of 13"

Post by Chris_C » 03 Apr 2014 03:00 pm

The offset is a measurement of where how far "in" to the wheel the mating face sits on the hub of the car. Because fwd cars have the transmission as well as the steering to deal with, this face is generally right against the outer face of the wheel (positive offset). On rwd, it's somewhere around the middle ish. (huge generalisation obviously, but it's a rule of thumb)

All it means is that the wheel will be sitting closer in to the centre line of the car, so could rub the inner arches on full lock, but that can and does have an affect on the steering geometry that was designed in at the factory.

Only image I can find quickly is this, which is a bit naff but might explain better than I've managed.
Image
'89(G) 340 GLE B172k
'03 S60 D5 SE, '91 (J) MX5, 1954 Cyclemaster
Ex:
'89(F) 340 GL F7R (ex B172k) - Fake -> SBKV 300 Runner Up 08, 12; '91(H) 340 GL B14.4E - Kar; '88(F) 360 GLT B200E - Jet -> BKV 300 Runner Up 09; '89(G) 360 GLT B200E - Beast

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Hell Driver
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Re: Safety question: 15" rims fitted instead of 13"

Post by Hell Driver » 03 Apr 2014 10:27 pm

I've run 15 inch, (vauxhall calibre) wheels on a 340 for a while before now (currently the car has 14 inch 440 wheels). No problems at the time, smooths out small potholes better! Also with the lower profile tyres 205mm wide at the rear and 195mm at the front the grip was better. Road noise/ surface vibration was incresed a lot however. Even with 195mm at the front I had to use a spacer ring to avoid fouling issues on strut.

One important thing to remember is that once the tread level gets close to 1.6mm (legal minimum) on bigger wider tyres, the increased area of contact will spread the weight of the car more than narrow smaller tyres (tyres cut through the water less) and could lead to you loosing the back end in wet conditions esp. with RWD. Something I noticed even in a front wheel drive 440 I had the wheels on for a while!!!

Make sure the tread is good on the tyres as the bigger wheels are often off bigger heavier cars!

The only reason I went down to 14 inch wheels with deeper walled tyres again was for comfort while towing the caravan and with family on board!
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SteveP
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Re: Safety question: 15" rims fitted instead of 13"

Post by SteveP » 04 Apr 2014 10:45 am

It should be absolutely fine, if anything it'll improve the road manners of the car in my experience. Even going from 175/70/13 to 185/65/14 made a big difference on my GLS and removed some of the slop you get with running such a tall profile (ride quality was great!). Quick tip if you do replace tyres 195/50/15 will also work and they're a lot cheaper. Only real downside I found was the wider tyres tended to be pretty much useless in snow, but that was probably down to tyre choice more than anything. Wheels with a 30-40mm offset range will work best.
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thododd
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Re: Safety question: 15" rims fitted instead of 13"

Post by thododd » 04 Apr 2014 08:11 pm

From a safety point of view my immediate areas of concern would be; PCD, offset, wheel bolt/nut taper and centrebore

being a rover you can be sure its the correct (4 x 100mm) PCD
Theres some room for error with offsets (more on some cars than others) so as long as the wheel doesnt have clearance issues with the suspension or brake calipers when bolted up and doesnt touch the arches when turning from lock to lock theyll be fine (novas, golfs, civics etc have similar ET to the 340 and are FWD.... 90's PSA cars have lower offset than many rwd cars)
The centrebore of the wheel is what 'aligns' it on the hub. If theres any difference it should be overcome by spigot rings (when the hub is smaller than the wheel cb) or by machining (to bring a smaller cb wheel out to the hubs diameter). Wheels with tapered bolt holes will centre themselves onto the hubs with the appropriate faced bolts but its not as ideal as spigot rings.
If the wheels have flat seated bolt holes theyll need flat faced nuts, using tapered nuts may damage the wheel.

if all the above check out, then crack on!

I prefer 15's on 300's, closes up the arch gap and gives a touch more ground clearance. 8) imo 13's look too small, like castors on a sofa

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