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Tyre size #661162
09/09/20 07:55 AM
09/09/20 07:55 AM
Joined: Jul 2017
Posts: 130
Cheshire
Chilliblu Offline OP
L - Learner Plates On
Chilliblu  Offline OP
L - Learner Plates On

Joined: Jul 2017
Posts: 130
Cheshire
Hi all

I know nothing about tyres so excuse my ignorance. I have a 2014 plus 4 with 195/60 R15 tyres on the wheels. These are now 6 year old Yokohama so i thought time to change.

Question is. Can I put a tyre on with a bigger depth? The car only just scrapes over some of the local speed restriction devices and wondered if i can fit a bigger tyre to raise the car a little?

If the answer is yes then what is the impact of doing so? does it alter handling and ride? will it impact the accuracy of the speedo? if so by how much? will the spare still fit?

Sorry if these are silly questions but as I said I know nothing about tyres other than they are round and black confused2

By the way any recommendations for what make if this is possible?


Last edited by Chilliblu; 09/09/20 09:28 AM.

Andy
2014 Morgan Plus 4
Re: Tyre size [Re: Chilliblu] #661175
09/09/20 08:31 AM
09/09/20 08:31 AM
Joined: Jul 2014
Posts: 580
Cornwall
griffo Offline
Talk Morgan Regular
griffo  Offline
Talk Morgan Regular

Joined: Jul 2014
Posts: 580
Cornwall
Hi,
I fitted 205/65/15 Avon ZV7 tyres to my 2014 Plus 4. No issues with clearance, slight increase in ride-height and they look better in the wheel arches. Also slight improvement in ride comfort (at 22 psi) with the higher sidewalls. No discernible change in handling.205/60/15 were standard on my Morgan alloy wheels -- maybe if u have wire wheels they fit skinier tyres as standard. Hope this helps.

Re: Tyre size [Re: Chilliblu] #661179
09/09/20 08:41 AM
09/09/20 08:41 AM
Joined: Sep 2014
Posts: 1,746
London
MOG 615 Offline
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MOG 615  Offline
Talk Morgan Enthusiast

Joined: Sep 2014
Posts: 1,746
London
There are no silly questions here , lots of stupid mistakes are made by not asking them.

There are various sites that will show you the difference in wheel diameter between the various sized tyres and what the effect will be on the speedo reading.

This is just one of them https://www.tyresave.co.uk/tyre-size-calculator/ and another https://www.tyremen.co.uk/tyre-size-calculator

By inputting the current size tyre and a possible alternative, you can get a very accurate idea of what is possible and the effect on the ride height and the speedo accuracy.

For instance using a 185/70 x 15 would give an increase in diameter of 1% , which is well within the accuracy needed to keep the speed-reading legal.

Look at the thread below on the Ferrari Blue +4 and the recommendations there are for the 165/80 x 15 Vredstein . This would almost 2% larger in diameter but less than 2% "fast" on the speedo at 70mph. It might be enough to help you with the infamous bumps, and will hep the ride quality of the car.

I too live in an area which is infested with speed bumps, and have to be very careful making a slow transit across them. You can adjust the ride height at the front of the car by fitting the SSL front suspension modification. Not cheap at almost £1000 including fitting, but a very worthwhile modification, and this is what I have done. I continue to use 205/60 x 15 on my +8 (but this is much too big for a +4)


Andy G
1999 +8 , Indigo Blue.
Ex-John McKecknie/Mike Duncan 1955 +4 racer.
Re: Tyre size [Re: Chilliblu] #661188
09/09/20 09:01 AM
09/09/20 09:01 AM
Joined: Sep 2009
Posts: 5,533
Köln Germany
Heinz Offline
Charter Member
Heinz  Offline
Charter Member

Joined: Sep 2009
Posts: 5,533
Köln Germany
Perhaps Peter (Gambalunga) will come forward on this. As far as I remember he changed his Plus 4 from 195/60/15 to 195/65/15 and was very happy with it because he gained more ground clearance.

It must be said that of all Trad Morgans, the Plus4 has the smallest diameter tyres. In 2010 MMC itself had made a change to another model. Until then the Roadster, at least the series 1, had 205/60/15 tyres on the aluminium rims. (Stainless steel spoke rims had 16 inch). With the Roadster Sport in 2010 they then changed to 205/65/15 ex works. But then to 15 inch painted spoke wheels.

In short, you can drive 195/65/15 without hesitation. You have the benefit of greater ground clearance. The gearbox is slightly longer due to the slightly larger tyre diameter. The speedometer is very easy to readjust, because it interprets the signal digitally.

But I wouldn't use wider tyres, because all Morgan wings are always cut quite precisely to the specific tyre width during construction. And the steering may feel more easy and relaxed when keeping 195 width.


'14 4/4 graphite grey
Re: Tyre size [Re: Chilliblu] #661195
09/09/20 09:20 AM
09/09/20 09:20 AM
Joined: Nov 2018
Posts: 2,466
Northants, UK
TBM Offline
Talk Morgan Expert
TBM  Offline
Talk Morgan Expert

Joined: Nov 2018
Posts: 2,466
Northants, UK
As I said on the other thread referenced below, I've got larger tyres (prev 165/80) on my 4/4. 205/65 rear and 195/65 front (Avon ZV7). I fitted wider wheels, and uprated rear suspension and fitted a panhard at the same time so some of the points will be down to this, or a combination of the two. Used the tyre calculator above to select a similar rolling radius of tyre

1. Much more sure footed - can throw it round roundabouts with more confidence and into corners at 10-15mph more than previously (route to work etc)
2. Greater ground clearance at rear - no longer scraping the numberplate on speed humps and inclines.
3. Speedo reads a little high at GPS 70mph, she reads at 75mph. However, this is only a 2mph increase as she always read a little high.
4. No difference in steering - I was anticipating a heavier feel. I used to run the previous Conti's at about 26psi as I found any lower and the steering got heavy. However I can easily run the Avon 195's at 22psi. Not sure why? May be to do with age of Conti's or difference in rubber?
5. Tyres fill the arches fine, the 205's protude a few mil, but still cover the tread when looking from above.
6. No interference with bodywork either by suspension travel or steering.
7. Tyres are a sensible price.
8. Think the wheels and tyres look fabulous smile



1972 4/4 4 seater
Too many ratty motorbikes
Re: Tyre size [Re: griffo] #661927
13/09/20 08:39 AM
13/09/20 08:39 AM
Joined: Jul 2019
Posts: 422
Surrey
K
Kevcaster Offline
Learner Plates Off!
Kevcaster  Offline
Learner Plates Off!
K

Joined: Jul 2019
Posts: 422
Surrey
Originally Posted by griffo
Hi,
I fitted 205/65/15 Avon ZV7 tyres to my 2014 Plus 4. No issues with clearance, slight increase in ride-height and they look better in the wheel arches. Also slight improvement in ride comfort (at 22 psi) with the higher sidewalls. No discernible change in handling.205/60/15 were standard on my Morgan alloy wheels -- maybe if u have wire wheels they fit skinier tyres as standard. Hope this helps.


+1
Best thing I did, the handling and ride were much improved by the bigger tyres. 205 65 15 Avon ZV7, wire wheels

Last edited by Kevcaster; 13/09/20 08:52 AM.

Kevin

2009 Morgan Plus 4 4 seater

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