wheel offset - differences between standard rims

Fatty · Postby **Fatty** » Mon Jun 09, 2008 7:08 pm

looking at the specs between the standard 4 x 100 rims (hence nc is irrelevant, sorry clive)

na6 rims 14 x 5.5 +45

na8 rims 14 x 6 +45

nb8a rims 15 x 6 +40

nb8b / c rims 16 x 6.5 +40

just curious about the change in offset that seems to occur at the change from na to nb model.

does the wider rim compensate at all for the change in offset?

what is a reasonable variation (performance wise) from the \"standard\" offset. ie i have a set of 14 x 6 +38 rims for my na6. will they be ok? and how is this calculated?? any info on offset would be appreciated . ie - increasing offset has X result.. decreasing offset has Y result ...

please refrain from any reference to what \"looks\" good as far as dish / offest etc goes... i'm only interested in facts not opinions.

and why isn't this info in the tech archive already?. i'm sure it's been discussed a fair bit but a search didn't find anything.

Juffa · Postby **Juffa** » Mon Jun 09, 2008 10:16 pm

Hey Fatty,

In no way do I claim to understand Offsets, or scrub radius...... rather than talk through my A$$ I will point you at the following link

http://www.miata.net/garage/offset.htm

The same info and more is in the Mazda Miata Performance Handbook. I have a copy if you want to borrow it.....as long as you promise not to store in a tool chest in the rain.

And another link ==>> http://www.miamivalleymiataclub.com/tec ... Wheels.pdf

Yet another ==>> http://www.locostusa.com/forums/viewtop ... a743a93e6b

Last but not least ==>> http://www.smithees-racetech.com.au/ackerman.html

J

Fatty · Postby **Fatty** » Mon Jun 09, 2008 11:05 pm

Juffa wrote: I have a copy if you want to borrow it.....as long as you promise not to store in a tool chest in the rain.

and i still haven't returned the rusty tools to you ....

*hangs head in shame*

we really should sort this out one day, i owe you some shiny new tools, or some money. let me know either way !

Locutus · Postby **Locutus** » Tue Jun 10, 2008 12:43 am

goodwin racing suggests that +38 is the minimum offset that shold be used on the street:

http://www.good-win-racing.com/Mazda-Pe ... Tires.html

Hammer · Postby **Hammer** » Tue Jun 10, 2008 6:04 pm

I've been looking for a +36 to +38 offset for my NB8B on 17\" for a while now to no avail. I'm looking at widening the track without resorting to wider wheels. I'd like to keep the size modest at 17x7s with the desired offset listed above.

Only way to get those offset for the 5 is getting them custom made by Simmons et al etc. Unfortunately Simmons design IMHO is old school(more suited to muscle cars etc.), and I don't know anyone else who does custom wheels.

All I find is factory standard offset (+40). But if someone has found wheels with lower than factory offset. I'd be very interested to know more.

Fatty · Postby **Fatty** » Tue Jun 10, 2008 6:43 pm

hammer, you could have a look for some toyota mr2 wheels. they share our stud pattern but are lower offset. i don't know if they make them in 17 tho .

kula · Postby **kula** » Tue Jun 10, 2008 6:48 pm

Hammer wrote:I've been looking for a +36 to +38 offset for my NB8B on 17" for a while now to no avail. I'm looking at widening the track without resorting to wider wheels. I'd like to keep the size modest at 17x7s with the desired offset listed above.

Only way to get those offset for the 5 is getting them custom made by Simmons et al etc. Unfortunately Simmons design IMHO is old school(more suited to muscle cars etc.), and I don't know anyone else who does custom wheels.

All I find is factory standard offset (+40). But if someone has found wheels with lower than factory offset. I'd be very interested to know more.

there are a fair few japanese rims available which suit...

try rays enkei and wedsport.
rayswheels.co.jp

they have 17x7 in heaps of styles in various offsets down to +13.
+30 is common too.

AB7 · Postby **AB7** » Wed Jun 11, 2008 6:11 am

Locutus wrote:goodwin racing suggests that +38 is the minimum offset that shold be used on the street:

http://www.good-win-racing.com/Mazda-Pe ... Tires.html

Thats on 8" wide rims, which is the same recommendation on 949 Racing.
On 7" rims, their recommendation is +25.

Alex · Postby **Alex** » Wed Jun 11, 2008 12:56 pm

hmm, I'm interested to know what the minimum offset could be used for 15x7's on an NB8A without rolling guards and at stock height and suspension set up (no crazy camber)

Locutus · Postby **Locutus** » Wed Jun 11, 2008 2:29 pm

AB7 wrote:Thats on 8" wide rims, which is the same recommendation on 949 Racing.
On 7" rims, their recommendation is +25.

i can't find any mention of rim width & offset correlation on either website. my guess is that they are recommending lower offset for wider wheels to prevent rubbing rather than preserve suspension geometry.

Damo · Postby **Damo** » Thu Jun 12, 2008 12:48 pm

Thanks for those links Juffa! Who knew all this stuff was so complicated? I'll just stick to the standard wheels for now.

wun911 · Postby **wun911** » Thu Jun 12, 2008 5:02 pm

Can you use a wheel spacer to help you \"predict/see\" the effects of decreasing the offset?

If you want to put +30 offset wheels you just go and put a 10mm wheel spacer? If you then like the 'results' you can go off and buy your new wheels.

(Of course there is added weight of the spacer itself)

Benny · Postby **Benny** » Thu Jun 12, 2008 6:21 pm

wun911 wrote:Can you use a wheel spacer to help you "predict/see" the effects of decreasing the offset?

If you want to put +30 offset wheels you just go and put a 10mm wheel spacer? If you then like the 'results' you can go off and buy your new wheels.

(Of course there is added weight of the spacer itself)

And the fact that wheel spacers are illegal on street cars.