Upgrading 14” to 16” wheels - a meaningful functional difference

[zinz]

One could go with a 15" wheel and the split the difference in size, but open up a plethora of choices on tires.

Ed Z

"... Jefe'... do you even know what a "plethora" is???"

 

[Markos]

I know you are speaking in general terms. However as wheel diameter increases, so does the width. You won’t find many 8x14“ factory wheels, and you won’t find a 7x17” wheel. The “series” of tire is the aspect ratio, or the percentage of the stated tire width. So a 225/50 (50% of 225mm) has a 112.5mm sidewall. A 205/55 has a 112.75mm sidewall.

Stan’s 225/60/14 have a 135mm sidewall. A factory 195/70/14 has a 136.5mm sidewall. This is a more relevant example because he kept 40’s, increased the width, and appropriately decreased the aspect ratio.

The only point of this is that when referring to 50/60/70 series tires, it is important that you are comparing the width. In general (as Scott suggested) it doesn’t matter, because we only play with a handful of known tire combinations.

If however, you are doing any custom wheel building it makes sense to actually pay attention to the aspect ratio.

in thinking of simple math (round numbers), say the tire diameter is 25", it is easy to calculate the nominal tire profile above the rim diameter
with 14" wheels, the tire profile is 5.5"
with 15" wheels, the tire profile is 5"
with 16" wheels, the tire profile is 4.5"
with 17" wheels, the tire profile is 4"
with 18" wheels, the tire profile is 3.5"

so generally 14" wheels for the e9 use 70 series tires / 15" wheels use 60 series tires / 16" wheels use 55/50 series tires / 17" wheels use 50/45/40 series tires and 18" probably use 45/40/35 series tires dependent on the width size available.

i thought about 17" with 50 / 45 series ... but 1.5' Sidewall profile difference ... for me 50 series tires are comfortable. 60 series are more comfortable and 70 series tend to slide a bit on really twisty mountain roads - @Stevehose, talk to us about Tail of the Dragon ... of course you were using the CN-36's which are much better than your basic grand touring all season tires.

 

[rsporsche]

I have always liked the a008 tires from a visual perspective. still prefer the look of the pirelli the most, just don't like the price in 15"

 

[Stan]

Yes the

@Stan you have the benefit of a lower profile tire (60 series) and a wider contact patch than the standard 14" tire. the tires are 9" wide and have a tread width of 7.6" ... which is narrower than the 16" tread width. since those tires have a more rounded shoulder, are your fender lips rolled and do you have camber plates. i will note that size is very limited. on tire rack, the goodrich is the only tire available in that size.

fender lips are rolled.
The tires are goodrich with the raised white letters blacked out and mounted inside.
When they time out I will likely go with Michelin XWX or some other tire with a more period look.
I will keep the 14" x 7 Alpina wheels.

 

[rsporsche]

I know you are speaking in general terms. However as wheel diameter increases, so does the width. You won’t find many 8x14“ factory wheels, and you won’t find a 7x17” wheel. The “series” of tire is the aspect ratio, or the percentage of the stated tire width. So a 225/50 (50% of 225mm) has a 112.5mm sidewall. A 205/55 has a 112.75mm sidewall.

Stan’s 225/60/14 have a 135mm sidewall. A factory 195/70/14 has a 136.5mm sidewall. This is a more relevant example because he kept 40’s, increased the width, and appropriately decreased the aspect ratio.

The only point of this is that when referring to 50/60/70 series tires, it is important that you are comparing the width. In general (as Scott suggested) it doesn’t matter, because we only play with a handful of known tire combinations.

If however, you are doing any custom wheel building it makes sense to actually pay attention to the aspect ratio.

yes Markos, i am speaking in generality. in 17" wheels, you can get 17" x 7" bbs rs / style 5 as a custom setup. just as i can get a 16" x 6" bbs rs wheel (to fit in the wheel well as a spare tire)

i am referring to tires that are in the general realm of 25" nominal diameter. for 17" wheels, there are 5 basic sizes - 205/50 + 215/45 for fronts, the others for rears - do they all fit? good question. @vince is using 225/45-17 fronts and 245/40-17 rears. if i went 17's i would go 205/50 + 225/45
205/50-17 (25.1" x 8.1"),
215/45-17 (24.6" x 8.5")
225/45-17 (25" x 8.9")
235/45-17 (25.3" x 9.3")
245/40-17 (24.7" x 9.8")

14" - as we know 195/70-14, 205/70-14. 225/60-14 (@Stan)
15" - 205/60-15 (limited availability) and 215/60-15
16" - 205/55-16 + 225/50-16 (staggered)

 

[adawil2002]

Andrew, you continue to be a bad influence on my life. No tires in your garage for those 14” rims?

Correct, John. No tires on either set of Mahles & both sets have center caps included. (Free delivery for you)

 

[rsporsche]

Andrew, i think your coupe looks perfect with the BBS RS 16s ... i think that either 15" or 16" wheels look the best (my opinion, might not be others) in relation to sidewall size. i think the polished lips do good things for certain colors on the coupe.

in relation to the harshness of ride, i think the solution is to go to coilovers with progressive springs and slightly softer springs. to me the stiff lowering springs make the setup seem harsher. i think softer progressive springs will be more comfortable on the initial bumps and stiffer once initially compressed ... perhaps being more predictable as well as comfortable overall.

 

[JFENG]

progressive springs and slightly softer springs

I personally don’t want to go to coil overs and don’t understand why it is needed to employ progressive rate springs.

Why couldn’t we just lobby CN to produce a second type of E9 spring, a progressive version, of his current springs which many of us use and enjoy? Or buy them for the Euro source recently identified in the FS thread on springs?

 

[Markos]

I personally don’t want to go to coil overs and don’t understand why it is needed to employ progressive rate springs.

Why couldn’t we just lobby CN to produce a second type of E9 spring, a progressive version, of his current springs which many of us use and enjoy? Or buy them for the Euro source recently identified in the FS thread on springs?

I agree. It’s just easier with coilovers because of the wide spring selection and standard sizing. The carb CSL had progressive springs back in 1972.

 

[rsporsche]

thanks for mentioning the euro source for H+R progressive springs John ... i forgot about those. i don't know what the spring rate options are though. i won't be going to coilovers anytime soon, but at some point i may. i think i will look into the H+R springs shortly. can't speak to CN, that's a business / market decision.

 

[Stevehose]

Borranis are sick!

Here’s my take from a 2002 perspective. My ‘71 came to me with 15” Panasports and 195/50 tires. It’s lowered, ST bars and Billy Sports. I put new Yoko S Drives and it was very sticky in the twisties. The ride was very firm.

A couple years ago I found some nice Borrani 13” steelies. I bought the CN36 Pirellis. Almost same overall diameter. Ride quality on modern roads was VERY much improved. Grip was still there and I’m not scared to throw it into any street corner.

My recommendation is keep the 14” for street, and use the 16” on the track.

 

[Stevehose]

I am not one to push my stock-ish car to the limits in corners, but I often exceed (allegedly) the posted highway speed limits. I have Bilsteins, CN lowering springs & neg camber plates, and Alpinas. The cn36 are great tires for aggressive touring and also in unfortunate times when incurring heavy rain at speed. I can’t comment on how they’d do in a drift. I will definitely buy them again in due course. Also, can’t beat their looks, they ooze a touch of vintage class.

60 series are more comfortable and 70 series tend to slide a bit on really twisty mountain roads - @Stevehose, talk to us about Tail of the Dragon ... of course you were using the CN-36's which are much better than your basic grand touring all season tires.

 

[JFENG]

I agree. It’s just easier with coilovers because of the wide spring selection and standard sizing. The carb CSL had progressive springs back in 1972.

Ah, I see.
I just looked on Summit and $65 gets you basically any spring size/rate in one of several std ID’s. That is less expensive, though the selection of progressive rate springs is limited. I found this helpful

Tech Tips | Motorsports Performance Handbook | Hyperco

Technical information and advice from the engineers at Hyperco, a leader in high-performance suspension springs and components.

www.hypercoils.com

 

[Markos]

Ah, I see.
I just looked on Summit and $65 gets you basically any spring size/rate in one of several std ID’s. That is less expensive, though the selection of progressive rate springs is limited. I found this helpful

Tech Tips | Motorsports Performance Handbook | Hyperco

Technical information and advice from the engineers at Hyperco, a leader in high-performance suspension springs and components.

www.hypercoils.com

Ahh yes, but lookup the tender spring used in conjunction with a linear spring. Not talking about a helper spring.

 

[adawil2002]

I am not one to push my stock-ish car to the limits in corners, but I often exceed (allegedly) the posted highway speed limits. I have Bilsteins, CN lowering springs & neg camber plates, and Alpinas. The cn36 are great tires for aggressive touring and also in unfortunate times when incurring heavy rain at speed. I can’t comment on how they’d do in a drift. I will definitely buy them again in due course. Also, can’t beat their looks, they ooze a touch of vintage class.

With that suspension set up, highly recommend the 22mm F & 19mm R, Suspension Techniques sway bars over the stock ones.

 

[Stevehose]

Do they bolt right in without mods? What are the benefits?

With that suspension set up, highly recommend the 22mm F & 19mm R, Suspension Techniques sway bars over the stock ones.

 

[Stan]

I am not one to push my stock-ish car to the limits in corners, but I often exceed (allegedly) the posted highway speed limits. I have Bilsteins, CN lowering springs & neg camber plates, and Alpinas. The cn36 are great tires for aggressive touring and also in unfortunate times when incurring heavy rain at speed. I can’t comment on how they’d do in a drift. I will definitely buy them again in due course. Also, can’t beat their looks, they ooze a touch of vintage class.

I think I may have exceeded the speed limits in your car! Easy to do and a lot of fun!

 

[adawil2002]

Do they bolt right in without mods? What are the benefits?

Yes, bolt on to the stock mounts, should come with poly bushings & clear grease. Poly is less compliant enabling the sway bar to be more responsive.

Benefits are immediately noticeable & significant. Much less body-roll keeping the car flatter & confident through curves & turns. More neutral steering, Coupes tend to understeer, throwing weight & momentum to the outside of the turn causing one to slow down, generally, cars are engineered this way. Lastly, increased stability at highway speeds. Athena handles similarly to my 1997 M3.

 

[JFENG]

Athena handles similarly to my 1997 M3.

I’d like to emphasize this post. Much of what the average enthusiast is looking for in terms of handling is not so much the peak grip achieved right before slip angles precipitously drop (skidding). I think what many of us look for are
(1) responsive - meaning when you make an input change into the steering, you prefer that the car responds with a directional change without lots of delay. Removing compliance from the suspension and tires helps a lot. Super low profile tires with shaved tread (no squirm) helps a lot, stiffer springs and higher damping shocks are also very helpful. Stiffer bars is another method that generally comes with less sacrifice in ride quality, but with less benefits for braking stability (as Andrew already mentioned).

(2) balance - meaning when you turn the steering a certain amount, you want the car to respond is a consistent and expected/ ‘linear’ fashion. Cars that understeer (E9) and oversteer (911) don’t feel balanced. Not balanced doesn’t mean not fast. It’s just requires more skill and effort to get the car to go where you want it.

Stiffer anti-sway bars help substantially with both goals. I happen to like the heavier ST bars and not going to really low profile tires and really strong springs/dampers.

Andrew, are you saying your E9 has equal grip to your M3, or that it has the same quality of handling feel?

 

[adawil2002]

M3, Athena & Vern all have similar handling characteristics. I don’t my push my car’s limits to 10/10ths. Mostly 5-7 & 8 when very spirited.