The Dunlop SP Sport 225/50 R17 94W tyres on my yeti 170 diesel will need replacing soon.

I am considering non- standard 215/55 R17 94W 's for 2 reasons.

1. £44 cost saving per tyre

2. Hoping that 55 profile will give a slightly softer ride than 50's.

Has anyone tried or considered this mod?

Will it improve ride quality?

Will it have any negative consequences?

I rang my insurer ( SAGA ) to ask if it would affect my cover. The girl rang the underwriter to check . The reply was that so long as the tyres were professionally made and fitted it would be OK.

I asked to speak to the underwriter but was told this was not possible. She also said confirmation of the ' permission ' in writing was not necessary as all calls are recorded.

Comments please....and thanks in anticipation!

If a tyre size is not listed in the manual it has not been type approved for the car, your insurance will be null and void if you make an accident. So be very, very careful in doing something like this. You could be cutting your nose to spite your face. And if they are accepting this, as you state, definitely get it in writing.

(I'm saying this without having checked The Plumber's Guide to tyre sizes mind)

Don't forget a 55 profile on 215 is basically the same 'depth' as as 50 on a 225 (only 1.7% larger) as profile numbers are a ratio, not a measurement so not sure how much softer it would actually feel.....

If a tyre size is not listed in the manual it has not been type approved for the car, your insurance will be null and void if you make an accident. So be very, very careful in doing something like this. You could be cutting your nose to spite your face. And if they are accepting to as you state definitely get it in writing.

(I'm saying this without checked The Plumber's Guide to tyre sizes mind)

Thanks for swift reply. I agree with you in spite of what the Saga rep said... but would not commit to writing.

Don't forget a 55 profile on 215 is basically the same 'depth' as as 50 on a 225 (only 1.7% larger) as profile numbers are a ratio, not a measurement so not sure how much softer it would actually feel.....

Thanks for swift reply and pointing out that 55 ( on a 215 ) is an aspect ratio so wall height would be hardly any different to a 50 ratio on a 225.

I would stick to the standard size, however would try an H rated all weather tyre such as the Nokian eNtyre or the Goodyear 4Season. Softer compound being both an all weather and a lower speed rating. W rated summer tyres have much less give particularly at lower temps.

Will be OK with an H on the early 170's with the first generation CR engines, as that speed rating is approved.

TP

There is a company who can raise the car ground clearance and also fitted 215/60R17 tyres, which made the car look better. I'm not commenting on anything else, but the tyres themselves gave an extra 16mm ground clearance and with the 25mm lift kit gave an impressive 42mm increase in ground clearance. There was a thread a few weeks ago about it.

Sent from my iPhone.

Nothing but good things to say about the GoodYear Vector 4 seasons for year round use.....unless you like to really give it some stick in the summer and want a "performance" summer tyre.

If a tyre size is not listed in the manual it has not been type approved for the car, your insurance will be null and void if you make an accident.

But, as we have discussed before, the manual does not list approved tyre sizes. It says that dealers "have access to the most current information", and, in respect of winter tyres, that permissible sizes "are stated in your vehicle documents" (which they aren't). And, as we have debated before, the German type approval lists are mandatory in Germany, not the UK.

But, as we have discussed before, the manual does not list approved tyre sizes. It says that dealers "have access to the most current information", and, in respect of winter tyres, that permissible sizes "are stated in your vehicle documents" (which they aren't). And, as we have debated before, the German type approval lists are mandatory in Germany, not the UK.

However those German lists are published for and by Skoda Germany (and carry the Skoda logo), therefore represent the manufactures approvals.

The owners handbook also lists the tyre sizes approved for the use of snow chains therefore those tyre sizes represent approved sizes.

I don't think it's by chance that both the handbook and the Skoda Germany guide list the same sizes.

TP

I would stick to the standard size, however would try an H rated all weather tyre such as the Nokian eNtyre or the Goodyear 4Season. Softer compound being both an all weather and a lower speed rating. W rated summer tyres have much less give particularly at lower temps.

Will be OK with an H on the early 170's with the first generation CR engines, as that speed rating is approved.

TP

Thanks for your advice. I didn't realise H rated were ok. ( where can I find that info. pls? ) Will investigate the Nokians you suggest.

Nothing but good things to say about the GoodYear Vector 4 seasons for year round use.....unless you like to really give it some stick in the summer and want a "performance" summer tyre.

Thanks for your advice. 4 seasons are often mentioned so I will investigate.

However those German lists are published for and by Skoda Germany (and carry the Skoda logo), therefore represent the manufactures approvals.

The owners handbook also lists the tyre sizes approved for the use of snow chains therefore those tyre sizes represent approved sizes.

I don't think it's by chance that both the handbook and the Skoda Germany guide list the same sizes.

Yes. But what Skoda Germany and TÜV Hessen say has no statutory force in the UK; it is merely a recommendation from another country. UK regulations do not recognise the concept of 'approved' tyres. What counts in the UK is whether the tyres fitted to a vehicle conform to the requirements of the Department of Transport's MOT test. On Class 4 vehicles (cars), the only requirement about tyre size and aspect ratio is that they must be the same for each tyre on the same axle. As for load index and speed rating, car tyres are not to be checked for those at all: such regulations apply only to Class 5 and 7 vehicles (those with more than 13 seats and HGVs respectively). In fact, if a MOT tester forms the opinion that a car tyre is of inadequate size, ply, or speed rating, he is specifically forbidden to issue a MOT failure on those grounds, but it is suggested he inform the person presenting the car for test of his opinion. There are no other regulations that would require the tester to confirm that tyres fitted to a vehicle presented for MOT comply with the vehicle manufacturer's recommendations, still less with some list published in Germany.

A car tyre that passes the MOT regulations as described above (plus, obviously, the other regulations about tread depth, damage, etc) is thereby certified to meet the minimum road safety standards required by law in the UK. If an insurer tried to argue that a tyre so certifed by the DOT's own test was inadequate or should not have been used or contributed to an accident, I'd invite him to meet me in court and be confident I could take him apart.

Is it still the case that a change in tyre size - or more specifically, a change in overall diameter and therefore circumference - equals a change in the speedometer reading?

Used to be that way when I were a lad putting 15" wheels on my Datsun that used to run 13"s. Had to take the car to a transmission specialist who would try various adapters where the speedo cable goes into the gearbox.

I'm not entirely sure I agree with some of the posts above. I'm with r999.

Like 4 Wheel Drive (I presume) I'm insured with Saga. I'm currently running 215/55-16 winter tyres on steel rims. Saga were quite happy with this and likewise said no need for anything in writing as the conversation was recorded. As an aside, they have also covered a tuning chip at no additional cost, simply marking my insurance certificate that he car has a modification.

In fact at the time I spoke to Saga, I could not get either 205/55 or 215/60 size tyres and the only way I could stay legal in Europe was the 215/55s.

Before fitting the above tyres, which had previously been on my Passat, I did some research and do far as I am aware, the over-riding legislation is the MOT requirement and this only says that the tyres must be of the same size and type (e.g radial) and obviously meeting the requirements for tread depth and damage. As r999 rightly says, speed index is not a part of the test since all tyres on sale meet a maximum speed rating that far exceeds the UK national limit. Moreover in Germany, there is a requirement to place a warning notice on the dashboard in sight of the driver where tyres of a lower speed rating than the national limit are fitted, hence the inclusion in the maxi dot display of an option to have a speed warning where lower rated winter tyres are fitted.

I'm not an expert (although I do run a 100 bus transport company) so each must satisfy his or her self on this.

John

Edited 23 February, 201214 yr by jst_at_home

Is it still the case that a change in tyre size - or more specifically, a change in overall diameter and therefore circumference - equals a change in the speedometer reading?

Used to be that way when I were a lad putting 15" wheels on my Datsun that used to run 13"s. Had to take the car to a transmission specialist who would try various adapters where the speedo cable goes into the gearbox.

Yes this is the case still, the speedo reading varies according to tyre size and aspect ratio. However the speedo in modern cars is electronic and you cannot use adapters to modify the cable drive. Modern cars tend to get the speed signal from other sources than the gearbox via various sensors, and adjustment usually involves removing the instrument cluster and replacing the speedo. If you look at a police car vRS, you'll see the calibrated speedo is very different to that fitted as standard.

I'm just highlighting what the manufacturer has approved as suitable for their particular vehicles, not what UK legislation dictates or for that matter challenging UK regulations.

From a personal point of view I'm just happier running what the manufacture thinks best suited to the Yeti in terms of size; tyres besides keeping you moving are a key aspect of car safety, hence now running tyres more suited to the changes in weather during the year.

However as some are aware from experience running the previous SE, I did question the suitability of the standard (in UK) 17" 225/50 wheel option for the roads I frequent, hence getting my current Monster built with the 16" set-up (as standard in CZ).

Regards,

TP

I would love to know how the 4x4 brigade cope with all this when they regular fit oversize wheels for using off road and even fitting the likes of 2" lift kits etc.....

Yes. But what Skoda Germany and TÜV Hessen say has no statutory force in the UK; it is merely a recommendation from another country. UK regulations do not recognise the concept of 'approved' tyres. What counts in the UK is whether the tyres fitted to a vehicle conform to the requirements of the Department of Transport's MOT test. On Class 4 vehicles (cars), the only requirement about tyre size and aspect ratio is that they must be the same for each tyre on the same axle. As for load index and speed rating, car tyres are not to be checked for those at all: such regulations apply only to Class 5 and 7 vehicles (those with more than 13 seats and HGVs respectively). In fact, if a MOT tester forms the opinion that a car tyre is of inadequate size, ply, or speed rating, he is specifically forbidden to issue a MOT failure on those grounds, but it is suggested he inform the person presenting the car for test of his opinion. There are no other regulations that would require the tester to confirm that tyres fitted to a vehicle presented for MOT comply with the vehicle manufacturer's recommendations, still less with some list published in Germany.

A car tyre that passes the MOT regulations as described above (plus, obviously, the other regulations about tread depth, damage, etc) is thereby certified to meet the minimum road safety standards required by law in the UK. If an insurer tried to argue that a tyre so certifed by the DOT's own test was inadequate or should not have been used or contributed to an accident, I'd invite him to meet me in court and be confident I could take him apart.

You learn something new every day! This all makes sense r999. How the EU has not had a say about things like this (yet) is a mystery I suspect.

I'm pretty confident that the law only requires that the fitted tyres are safe. Known unsafe ones-bald (in the sense of having less than the legal tread over the prescribed width), damaged (bulges/splits) are easy to define. It may also amount to dangerous driving if the tyres are such that driving on them amounts to and obvious risk to people or property. As examples I would suggest dangerously under or over inflated or of a size which substantially extends beyond the body work so as to present a hazard. If the tyre is in good condition and plainly capable of supporting the vehicle and not such as to cause road holding difficulties I cannot envisage any legal issues-criminal or civil.

Speed limited space savers driven at much above their design speed may be an issue.

In Germany and perhaps elsewhere in the world there are type approval regulations which restrict modifications and may even extend as far as limiting the use of tyres which do not match the makers O/E specs.

Insurers are entitled to know of any modification which may affect the risk they have agreed to cover-and the only way to be sure is to tell them if you change any substantial item. With motorcycles a common attitude is that if mods do not increase power beyond 5% they will cover without loading but that they will only repair or replace with manufacturers standard parts-so they will replace £2.5 k carbon fibre wheels with O/E items.

The law in the UK is not an issue for those who wish to use tyres other than in recommended sizes -certainly in the range of sizes so far discussed here.

You learn something new every day! This all makes sense r999. How the EU has not had a say about things like this (yet) is a mystery I suspect.

I suspect they would if they could.

Here's another bit of Euro nonsense.

They have plans to have roadside equipment in Europe to check if heavy vehicles have a working tachograph on board. Note that they of want to know if the tachographs is working, not if the driver has broken the law.

Here's another one I heard on Monday. If a VOSA examiner is checking a vehicle, he may look at the brake fluid reservoir. If it is clear plastic, he will check the level. If it is opaque or back, he won't open it to check the level, he'll just ignore it.

John