ARB shape - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

gpvecchi · 01-01-2021, 10:26 AM

I just discovered that the 86 GRMN uses a 15 mm rear ARB like facelifted models, but with different shape.
Is there some expert that can explain what would change?

DarkPira7e · 01-01-2021, 10:47 AM

The bar may have the shape to give access to the bolts on the rear diff mount

JD001 · 01-01-2021, 11:14 AM

Cost cutting, less kinks = less material.

norcalpb · 01-01-2021, 03:22 PM

I wonder if having the "bend" closer to the bushings causes the bar to have a lower spring rate? Maybe more? Good find though.

I'm curious to see if the rear endlinks are different because look at the intense angles of the bar ends compared to stock. Makes me almost think theres like a 1" GR endlink or something.

SCFD · 01-01-2021, 08:29 PM

This is interesting as I can't think of another example where different ARB geometries are used on the same vehicle.

I'm not sure why they would change the geometry but the change may result in a different spring rate.

gpvecchi · 01-02-2021, 03:37 AM

To clarify, the GRMN is the black one, the yellow is a JDM TRD, same shape of the OEM.
Endlinks are different, too. It's my opinion that the spring rate changes, too, but I think there is something else, or a different diameter will be sufficient.
My two cents: shorter lever, stiffer spring.

marco_mc22 · 01-02-2021, 03:51 AM

Maybe some clearance issues with a different differential or bracing? Always good find from you though

NLSP · 01-02-2021, 06:36 AM

Might be for clearance around what appears to be a subframe brace:

churchx · 01-02-2021, 08:34 AM

Somehow exhaust headers in this pic reminded me of facehuggers from "Alien"

gpvecchi · 01-02-2021, 09:01 AM

Nope, I have all the GRMN bracing, no interference.
Differential has the same housing, just 4.3 ratio and different TBR.

NoHaveMSG · 01-02-2021, 12:28 PM

Quote:

Originally Posted by gpvecchi

To clarify, the GRMN is the black one, the yellow is a JDM TRD, same shape of the OEM.
Endlinks are different, too. It's my opinion that the spring rate changes, too, but I think there is something else, or a different diameter will be sufficient.
My two cents: shorter lever, stiffer spring.

The rate of a spring is a pretty simple formula. It essentially comes down to the tensile strength of the material X material thickness and then factored by it's length. If the goal was to just decrease the spring rate it would be simpler to go to a smaller diameter. I wonder if they were having an issue with breakage and had to go to gentler bends.

churchx · 01-02-2021, 01:50 PM

But if bar is longer due extra bends, even of same material & thickness it should be easier to bend, no? Though in this case clearance of bracing sounds right reasoning.

NoHaveMSG · 01-02-2021, 02:03 PM

Quote:

Originally Posted by churchx

But if bar is longer due extra bends, even of same material & thickness it should be easier to bend, no? Though in this case clearance of bracing sounds right reasoning.

Correct, but if the goal is to make it easier to bend(reduce spring rate) then why not just make it smaller? I think the issue is durability. Either the thickness of the bar doesn't like that bend, or a smaller bar is not durable enough so they went to a larger one and added more lever to it.

I don't think clearance is an issue. The bar is not really in the way of anything.

Here is the subframe with everything mounted out of the car. Not a great pic but there is no clearance issue that I have noticed.

marco_mc22 · 01-02-2021, 02:25 PM

Quote:

Originally Posted by gpvecchi

To clarify, the GRMN is the black one, the yellow is a JDM TRD, same shape of the OEM.
Endlinks are different, too. It's my opinion that the spring rate changes, too, but I think there is something else, or a different diameter will be sufficient.
My two cents: shorter lever, stiffer spring.

Maybe a bit stiffer with less weight instead of a larger one?

01-01-2021, 10:26 AM	#1
gpvecchi Senior Member Join Date: Mar 2018 Drives: Toyota 86 GT Limited PP (Model G) Location: Italy Posts: 1,052 Thanks: 414 Thanked 359 Times in 202 Posts Mentioned: 14 Post(s)	ARB shape I just discovered that the 86 GRMN uses a 15 mm rear ARB like facelifted models, but with different shape. Is there some expert that can explain what would change?

01-01-2021, 10:47 AM	#2
DarkPira7e Rust bucket enthusiast Join Date: Feb 2017 Drives: 2013 Turbo Firestorm FRS Location: Vermont Posts: 4,075 Thanks: 3,341 Thanked 4,227 Times in 2,124 Posts Mentioned: 33 Post(s)	The bar may have the shape to give access to the bolts on the rear diff mount __________________ Turbo FR-S Build - Build Thread JDL EL Recirc manifold, Boostlab BL58x Turbo w/ T51R, 17x9 ARC-8, IAG block

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01-01-2021, 11:14 AM	#3
JD001 Senior Member Join Date: Apr 2015 Drives: Subaru BRZ Location: UK Posts: 6,270 Thanks: 7,988 Thanked 6,512 Times in 3,646 Posts Mentioned: 26 Post(s)	Cost cutting, less kinks = less material.

01-01-2021, 03:22 PM	#4
norcalpb Senior Member Join Date: Oct 2013 Drives: 2013 BRZ, 2023 Model 3 Location: SF Bay Area Posts: 2,347 Thanks: 1,256 Thanked 904 Times in 591 Posts Mentioned: 15 Post(s)	I wonder if having the "bend" closer to the bushings causes the bar to have a lower spring rate? Maybe more? Good find though. I'm curious to see if the rear endlinks are different because look at the intense angles of the bar ends compared to stock. Makes me almost think theres like a 1" GR endlink or something.

01-01-2021, 08:29 PM	#5
SCFD Senior Member Join Date: Sep 2020 Drives: FR-S Location: USA Posts: 171 Thanks: 322 Thanked 71 Times in 50 Posts Mentioned: 2 Post(s)	This is interesting as I can't think of another example where different ARB geometries are used on the same vehicle. I'm not sure why they would change the geometry but the change may result in a different spring rate.

01-02-2021, 03:37 AM	#6
gpvecchi Senior Member Join Date: Mar 2018 Drives: Toyota 86 GT Limited PP (Model G) Location: Italy Posts: 1,052 Thanks: 414 Thanked 359 Times in 202 Posts Mentioned: 14 Post(s)	To clarify, the GRMN is the black one, the yellow is a JDM TRD, same shape of the OEM. Endlinks are different, too. It's my opinion that the spring rate changes, too, but I think there is something else, or a different diameter will be sufficient. My two cents: shorter lever, stiffer spring.

01-02-2021, 03:51 AM	#7
marco_mc22 Senior Member Join Date: Jun 2017 Drives: Toyota 86 Location: Italy Posts: 139 Thanks: 42 Thanked 74 Times in 57 Posts Mentioned: 2 Post(s)	Maybe some clearance issues with a different differential or bracing? Always good find from you though

01-02-2021, 06:36 AM	#8
NLSP Senior Member Join Date: Dec 2013 Drives: 2014 Ultramarine FR-S Location: Vancouver, BC Posts: 520 Thanks: 427 Thanked 558 Times in 246 Posts Mentioned: 2 Post(s)	Might be for clearance around what appears to be a subframe brace:

01-02-2021, 08:34 AM	#9
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,336 Thanks: 698 Thanked 2,091 Times in 1,437 Posts Mentioned: 53 Post(s)	Somehow exhaust headers in this pic reminded me of facehuggers from "Alien"

01-02-2021, 09:01 AM	#10
gpvecchi Senior Member Join Date: Mar 2018 Drives: Toyota 86 GT Limited PP (Model G) Location: Italy Posts: 1,052 Thanks: 414 Thanked 359 Times in 202 Posts Mentioned: 14 Post(s)	Nope, I have all the GRMN bracing, no interference. Differential has the same housing, just 4.3 ratio and different TBR.

01-02-2021, 01:50 PM	#12
churchx Senior Member Join Date: Mar 2015 Drives: 2014 GT86 Location: Latvia, Riga Posts: 4,336 Thanks: 698 Thanked 2,091 Times in 1,437 Posts Mentioned: 53 Post(s)	But if bar is longer due extra bends, even of same material & thickness it should be easier to bend, no? Though in this case clearance of bracing sounds right reasoning.

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