Mazda Rotary Club

General => General Technical => Topic started by: FD3S Efini on September 23, 2010, 05:42:27 PM

Title: I dont understand ET
Post by: FD3S Efini on September 23, 2010, 05:42:27 PM
ok im leaving myself open to all kinds of abuse here lol
 
ok im looking at getting a new set of alloys for the FD and i have been looking on the internet at new wheels and i dont understand how the ET is measured can anyone simplify it for me and what sort of ET i should get to give the car an agressive stance,
 
all help is much apreciated....please school me lol
 
Kris
Title: I dont understand ET
Post by: dthebuk on September 23, 2010, 05:50:27 PM
ET or offest is the distance (mm) from centre line of the wheel (width ways) to the surface which mates up with the hub. For an aggressive stance you want a lowish or negative offset.

But if you have a 9j and an 8J with the same offset, the 9J will poke more.

I run 9J et 38\'s on my FC and they sit just about flush. Though i think the FD requires a slightly lower offset. So for a 9J wheel on the rear I\'d suggest something along the lines of a +20 or +30 offset or something inbetween. Fit the wheels and then decided on the right tires to match.

TBH to work out the right width and offset, the best Idea is to measure the distance between the hub and the arch, decide what width you want, and then calculate what kind of offset you need. Or If you already have wheels and want them to be more aggressive, you could just buy spacers
Title: I dont understand ET
Post by: yehreally on September 23, 2010, 06:00:31 PM
I don\'t understand ET either....... Whats a JJ on an 8JJ or a 9JJ compared to a J ?
 
(http://i.telegraph.co.uk/telegraph/multimedia/archive/01592/ET_1592627c.jpg)
Title: I dont understand ET
Post by: FD3S Efini on September 23, 2010, 06:06:24 PM
so if i measure from the hub to the wheel arch then thats what et i should get closest to?
 
sorry if im a bit slow im looking at getting some ultralite wheels in the near future and wanna make sure it looks agressive enough,
 
also if i went from 17 inch to 18 inch wheels will there be much of an effect on performance and handling of the car?
 
Cheers
 
Kris
Title: I dont understand ET
Post by: batman on September 23, 2010, 06:23:59 PM
its a bad thing when some one posts this but im glad there have been no bad posts no one should be affraid to ask good for you fds
Title: I dont understand ET
Post by: FD3S Efini on September 23, 2010, 06:45:40 PM
cheers bud
 
reason im asking is because i want to get some new alloys and i dont want them to hide in the wheel arches where no one can see them and make the car look shocking,
 
the alloys im interested are http://www.ultralitewheels.com/nurburgring.htm
 
Hopefully the info still keeps coming as im still a little unsure,
 
Cheers
 
Kris
 
P.S 700 Posts lol how time flys
Title: I dont understand ET
Post by: L18M on September 23, 2010, 06:50:39 PM
what you can do is measure the distance between your wheels and arches now.
then take your wheel off and see what the et on that is.

example.
(A) if your wheel sticks in by 15mm and your current is +40 then to get the wheel flush, you need to minus 15 from the et giving new et of 25.
(B) if you want the wheel to stick out say by 15mm then you would need et10 on your new wheels.

dont forget that if you find a nice set of wheels you like that do not have the et you wish then you can always add a bolt on spacer if need be.
for example (A) if you wanted the current wheels to fit flush then just add a 15mm bolt on spacer.

hth :)
Title: I dont understand ET
Post by: FD3S Efini on September 23, 2010, 06:53:45 PM
so pretty much the lower the ET is the more it sticks out?
 
whats the max ET an FD can have on the front and rear without wheels or tyres starting to rub or hit the car?
 
also are 18\'s to big for an FD and will they ruin the handling or make the car feel slower?
 
Kris
Title: I dont understand ET
Post by: dthebuk on September 23, 2010, 07:01:42 PM
The distance from the hub to the lip of the wheel is;

[1/2 x (wheel width)] - (ET)

so for a 9J wheel with ET 20 the distance from the hub to the outer wheel lip is (4.5 inches in mm) 110.25 - 20 = 90.25 mm  or around 3.55 inches

So measure the hub to arch gap, then choose a width and ET which is as close as possible.

To make things worse this will all change with a low car running negative camber, but it should put you in the right area
Title: I dont understand ET
Post by: L18M on September 23, 2010, 07:03:44 PM
18 will fit fd ok. will have lower profile tyre so less sideways movement than 17".
ideally be good to have 17" on frond and 18" on rear.
17" being lighter for better steering (thats what i\'ve read)
lower profile also means less rubber to take up bumps so will be bit harder ride.
Title: I dont understand ET
Post by: dthebuk on September 23, 2010, 07:10:03 PM
Quote from: yehreally;717739I don\'t understand ET either....... Whats a JJ on an 8JJ or a 9JJ compared to a J ?
 

dunno what JJ is about. But the J is just a reference to width. JJ is the same as J i believe. probably a typo
Title: I dont understand ET
Post by: FD3S Efini on September 23, 2010, 07:12:03 PM
cool think i got the basics now but need to do a little more research so i dont get the wrong alloys and waste money
 
Kris
Title: I dont understand ET
Post by: dthebuk on September 23, 2010, 08:06:30 PM
well if you want to measure that hub-arch gap I\'ll spec you some sizes mate
Title: I dont understand ET
Post by: yehreally on September 23, 2010, 08:11:55 PM
Ultralite do a ready made wheels for the FD which I believe is ET 35 could call and ask Contact Ultralite Wheels 01772 299826
Title: I dont understand ET
Post by: FD3S Efini on September 23, 2010, 08:16:12 PM
sweet il give them a call sometime this weekend and see what they can do for me cheers bud
 
Kris
Title: I dont understand ET
Post by: Prof on September 23, 2010, 09:57:17 PM
You want the tyre bible - awesome source of info for all things wheels and tyres :
 
http://www.carbibles.com/tyre_bible_pg4.html
 
Links at the bottom take you to the other pages.
Title: I dont understand ET
Post by: turbotoaster on September 23, 2010, 11:13:30 PM
if your looking at the nurburgrings like i did go for the 18x9.5 et35 front and rear, that way you will get a nice dish and be able to run decent tires, say 265 to 275 all around giving you loads of grip and able to rotate your wheels around to even out wear
Title: I dont understand ET
Post by: yehreally on September 23, 2010, 11:19:20 PM
be interested in seeing a pic of that :Thumbsup! any rub ?
 
Quote from: turbotoaster;717823if your looking at the nurburgrings like i did go for the 18x9.5 et35 front and rear, that way you will get a nice dish and be able to run decent tires, say 265 to 275 all around giving you loads of grip and able to rotate your wheels around to even out wear
Title: I dont understand ET
Post by: SiH on September 24, 2010, 07:00:42 AM
TBH the best way to sort it out is to try different wheels and see, if you can. One man\'s meat is another man\'s pickle sandwich.
So many variables affect how a wheel fits - ride height, camber, tyre size etc.

//www.rimtuck.com has a fair few FD\'s on it. Also worth looking at other people\'s cars and seeing what look you like. If you then post a photo up here then people can suggest where to go from there :)

Are you willing to do archwork? If you want a flush look you\'ll have to work the arches at least a little - a small lip roll on the rear will allow you good fitment with no troublesome rubbing.
Tyre size is also key - are you happy to run stretch, or do you want a full width tyre?

I wouldn\'t recomment the same setup all way round - because of the track on an FD, it will make the car look unbalanced - front will sit further out than the rears.

Also, bear in mind with this thread that you\'ve opened yourself up to a whole bunch of abuse from people who think that:
a) Stretched tyres are the root of all evil
b) some people\'s definition of \'flush\' is very different to others
c) anything that\'s not a wheel tucked away in an arch apparently looks stupid.

I love stupid.
Title: I dont understand ET
Post by: batman on September 24, 2010, 07:36:46 AM
Quote from: FD3S Efini;717746cheers bud
 
reason im asking is because i want to get some new alloys and i dont want them to hide in the wheel arches where no one can see them and make the car look shocking,
 
the alloys im interested are http://www.ultralitewheels.com/nurburgring.htm
 
Hopefully the info still keeps coming as im still a little unsure,
 
Cheers
 
Kris
 
P.S 700 Posts lol how time flys

 
nice rims but sod cleaning in between all those spokes lol i like these too
http://www.ultralitewheels.com/daiki-r.htm
Title: I dont understand ET
Post by: turbotoaster on September 24, 2010, 01:17:35 PM
like SiH says alot of it is about how important looks are to performance, run a average ride height and you can have wide wheels and tires all around, want the car on its arse then you cant without really high offsets.
 
what do you want to the car for?
Title: I dont understand ET
Post by: FD3S Efini on September 24, 2010, 03:13:04 PM
for the car i dont want the wheels to hinder the performance or the handling, its a shame that they dont do the wheels in 17\'s otherwise id have them, the only other option is the BBS LM\'s in 17 but they are uber expensive
 
Kris
Title: I dont understand ET
Post by: SiH on September 24, 2010, 03:45:06 PM
You can still run decent wheels in decent offsets with full width tyres. Witha  lip roll you should be able to pull of a mid 20\'s offset on the rear with a 255, for instance.

I run et25 front, et10(ish, long story!) rear with a 225 front and 235 rear, but it\'s a D01j/88 combo - it will walk all over a lot of full width tyre setups due to the tyre choice, but obviously there are wet weather/wear payoffs. For e that\'s fine though. It performs brilliantly and looks ace in my eyes, which is what counts to me :)
Title: I dont understand ET
Post by: FD3S Efini on September 24, 2010, 03:49:16 PM
you got any pics sih so i could have a butchers please bud
 
Kris
Title: I dont understand ET
Post by: captainbizzaro on September 24, 2010, 06:26:00 PM
This should help you get your head around the different paremeters

http://www.rimsntires.com/rt_specs.jsp