Mazda Rotary Club

General => General Technical => Wheels & Tyres, Suspension & Brakes => Topic started by: Cally on March 07, 2007, 11:42:37 AM

Title: Just bought some 18" alloys...
Post by: Cally on March 07, 2007, 11:42:37 AM
and need tyres as the rims will be here tommorrow. Bought some ultralite taka\'s in 18" - 8.5" fronts and 9.5" rears.

Does anyone know what tyre size I am best to run as I dont know what width etc is needed for an FD. Cheers.
Title: Just bought some 18" alloys...
Post by: G@NDY on March 07, 2007, 11:52:35 AM
I would have thought 235 and 255 matey
Title: Just bought some 18" alloys...
Post by: ace-rx7 on March 07, 2007, 12:03:08 PM
it seems that
235/40/18 front and 255/35/18 rears is the norm.
Title: Just bought some 18" alloys...
Post by: Cally on March 07, 2007, 12:03:24 PM
yer thats what I thought but was unsure on the right profile so I dont have any problems with rubbing etc
Title: Just bought some 18" alloys...
Post by: mikeyh on March 07, 2007, 12:34:01 PM
is the car lowered or anything cally?
im running 265 40/17`s the now but its standard hieight
Title: Just bought some 18" alloys...
Post by: Cally on March 07, 2007, 02:57:07 PM
yeah its lowered, about 40/50mm
Title: Just bought some 18" alloys...
Post by: n4bes on March 07, 2007, 09:22:16 PM
MikeyH and myself were discussing this...........................:xconfused

Why have 35 profile rear but 40 profile front.........???????????

I have 235/40 front and 265/35 rears, but dunno why not 40 or 35 all round.
Title: Just bought some 18" alloys...
Post by: d-king on March 07, 2007, 09:29:26 PM
if you have 235/40/18 on the front you should really have 265/40/18 on the rears because otherwise your rolling radius will be incorrect :0)
Title: Just bought some 18" alloys...
Post by: n4bes on March 07, 2007, 09:33:17 PM
Quote from: d-kingif you have 235/40/18 on the front you should really have 265/40/18 on the rears because otherwise your rolling radius will be incorrect :0)

I have done the calcs and you are only 1.25mm of difference................

Wonder if it\'s a cost and availability thing....???????
Title: Just bought some 18" alloys...
Post by: Archbish on March 07, 2007, 09:33:44 PM
the 35 is a percentage of the width of the tread.  So you would need to have 35% of 265mm to match 40% of 235mm tread.
Title: Just bought some 18" alloys...
Post by: Rixio on March 07, 2007, 09:35:06 PM
As D King said the rolling radius what be off...35 at the front will equal out to 40 atr :)
Title: Just bought some 18" alloys...
Post by: n4bes on March 07, 2007, 09:39:50 PM
Quote from: RixioAs D King said the rolling radius what be off...35 at the front will equal out to 40 atr :)


Don\'t think it\'s that bud. If you matched the wall size on the rears with the front the rolling radius would be out by 12mm. It is only out by 1.25mm at the moment.

If anything the reason is to componsate for the width of the rear as Arcbish said.....???????
Title: Just bought some 18" alloys...
Post by: d-king on March 07, 2007, 09:48:28 PM
i was told when i bought my rims that if i had 255/40/18 on the rear the rolling radius would be off but with 265 it was almost spot on to the front , ive no idea as i failed maths bigtime so only going bt what i was told lol ???
Title: Just bought some 18" alloys...
Post by: Archbish on March 07, 2007, 09:50:32 PM
bit more info here...

http://www.tyres-online.co.uk/techinfo/aspect_ratio.asp
Title: Just bought some 18" alloys...
Post by: n4bes on March 07, 2007, 09:54:38 PM
Quote from: d-kingi was told when i bought my rims that if i had 255/40/18 on the rear the rolling radius would be off but with 265 it was almost spot on to the front , ive no idea as i failed maths bigtime so only going bt what i was told lol ???


The size of the tyre is as follows bud.............

The wall is determined as a % of the width i.e

265mm wide 40% of that is 106mm
235mm wide 40% of that is  94mm

Hence 12mm rolling radius difference

265mm wide 35% of that is 92.75mm

Hence 1.25mm rolling road Difference

HTH mate.
Title: Just bought some 18" alloys...
Post by: Cally on March 07, 2007, 10:32:40 PM
Right so what tyres should I order? lol
Title: Just bought some 18" alloys...
Post by: n4bes on March 07, 2007, 10:37:52 PM
Quote from: CallyRight so what tyres should I order? lol

Probably.......................

225/40/18 F 255/35/18 R

OR

235/40/18 F 265/35/18 R

This keeps the rolling radius similar.........Imho.
Title: Just bought some 18" alloys...
Post by: Cally on March 07, 2007, 11:32:38 PM
prolly go 235 and 265 then, will I have any problems with rubbing on the rear with those sizes?
Title: Just bought some 18" alloys...
Post by: n4bes on March 07, 2007, 11:38:23 PM
That\'s wot I have on mine. Dunno wot offset the wheel are tho.

I\'ve got Bilstein suspension and new rear bushes fitted and it\'s solid. I don\'t get any rub at all.
Title: Just bought some 18" alloys...
Post by: Cally on March 08, 2007, 05:39:06 PM
Think I will go for 235/40/18 and 265/35/18 then, cheers for the help.
Title: Just bought some 18" alloys...
Post by: 20B_boy on March 08, 2007, 05:58:53 PM
What offsets did u order?
Title: Just bought some 18" alloys...
Post by: Cally on March 08, 2007, 06:12:11 PM
18x9.5 and 18x8.5 et35

http://smg.photobucket.com/albums/v669/rorybmw/cally/?action=view¤t=wheels1.jpg (http://smg.photobucket.com/albums/v669/rorybmw/cally/?action=view¤t=wheels1.jpg)
Title: Just bought some 18" alloys...
Post by: NurburgRob on March 08, 2007, 06:25:28 PM
I\'ve been looking at Ultralite wheel today too, was also wondering what offset and tyre size I shouls be going for.

Can someone confirm the offset for these size wheels?

Tar :)
Title: Just bought some 18" alloys...
Post by: PIPFC on March 08, 2007, 06:48:58 PM
offset should be 35 all round. that\'s what i have
Title: Just bought some 18" alloys...
Post by: NurburgRob on March 08, 2007, 07:42:22 PM
Sweeeeeet!!!!! get my bonus end of March, 18\'s here we come!

Who\'s doing the best prices on Ultralites? anyone?
Title: Just bought some 18" alloys...
Post by: 20B_boy on March 08, 2007, 08:09:16 PM
Stock FD offset is 50 all round i tihnk? I have 35/38\'s on mine and they dont sit inside the arches well imo...
Title: Just bought some 18" alloys...
Post by: sonyaddict on March 14, 2007, 08:52:03 PM
Quote from: Callyand need tyres as the rims will be here tommorrow. Bought some ultralite taka\'s in 18" - 8.5" fronts and 9.5" rears.

Does anyone know what tyre size I am best to run as I dont know what width etc is needed for an FD. Cheers.

Sorry to post this again...

18 & 17 Rex tyres..

225,40x18 matched to 255,35x18 (Fine)
or
235,40x18 matched to 265,35x18 (OK on an ET35 Rim Dodgy on ET30)

Then

225,45x17 matched to 255,40x17
or
235,45x17 matched to 265,40x17

Keeping rolling radius/tyre diameter the same as each other.

Tell me to nob off if you like ....  

Sonyaddict
(Ultralite Wheels)
Title: Just bought some 18" alloys...
Post by: RobbieRX-7 on March 14, 2007, 09:49:59 PM
How much did these wheels and tyres cost you cally and what tyres did you go for in the end cally? Any pics of them on the fd?
Title: Just bought some 18" alloys...
Post by: Cally on March 14, 2007, 11:49:29 PM
Not bought tyres yet but will be getting toyos 235x40x18 front, 265x35x18 rears. Wheels were around the £700 mark.
Title: Just bought some 18" alloys...
Post by: sonyaddict on March 15, 2007, 07:51:31 AM
If you want to advertise your business here then sign up as a vendor.

If you continue to ignore the rules we will ban you from accessing MRC which would be a shame all round.
Title: Just bought some 18" alloys...
Post by: NurburgRob on March 15, 2007, 10:10:14 PM
Quote from: sonyaddictME!:Giggle

Im trying to put together a group buy.

Come to Daddy :Thumbsup!

guy@japshop.co.uk


Cool, I\'ve seen the other thread.  I\'m needing wheels, tyres, bolts, locking bolts and spigot rings if required.

If there is no group buy (great if there is) can you do me an all in price on the new ATEC II in 18s for the FD.

Top Man!
Title: Just bought some 18" alloys...
Post by: merlyn on March 15, 2007, 10:25:22 PM
forget the physics guff!
i\'m driving 18x8.5\'s with 235/40x18s and the speedo is spot on according to the GPS. If you want to go larger (I do so i found out) you need 265/35x18s.
look up elite\'s website in dagenham (elitedirect.com) and they have a tyre conversion chart to tell you which tyres fir and how much faster or slower you will actually be travelling compared to your clock.
HTH
Pete
Title: Just bought some 18" alloys...
Post by: 20B_boy on March 15, 2007, 10:51:30 PM
Continuing the offset theme, assuming you are moving from a stock 8" rim to a 9.5" with a 35 offset, the outer edge is going to poke out nearly 35mm further. Go to a 10" at the back and you are 40mm further out...

This is why my rear tyres have wheel arch paint and rub marks on them (and the lips are already rolled over). Low offsets are probably fine if you are not driving that hard, but if you are going to do a lot of track time I\'d suggest going for a more suitable offset (or harsh a/r bars and rock springs so the wheels dont move! :Hammer). I\'m going to change as I want to get less ride hieght and with the present rims my 888s will be toast in a couple of hard corners :Thumbs-up

I think lol, am I wrong?!
Title: Just bought some 18" alloys...
Post by: NurburgRob on March 15, 2007, 11:02:24 PM
I agree, I\'m not convinced about the offset.

My standard front wheels are 17 x 8 with a 50 offset and they aren\'t that far away from the arch with standard suspension!

An 18 x 8.5 with 35 offset and lowered? there could be trouble ahead!
Title: Just bought some 18" alloys...
Post by: sonyaddict on March 16, 2007, 11:33:37 PM
If you want to advertise your business here then sign up as a vendor.

If you continue to ignore the rules we will ban you from accessing MRC which would be a shame all round.
Title: Just bought some 18" alloys...
Post by: RobbieRX-7 on March 16, 2007, 11:55:41 PM
Think this will clear things up a little