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Project Nissan B15 Sentra Spec-V
Project Nissan Sentra Spec-V part 5; Lessons in Geometry

By Mike Kojima

Although Nissan hyped up the Sentra Spec-V as a performance sedan in its marketing campaign, in truth the car was a little more than a piece of basic transportation with a few performance enhancing bells and whistles.  The car was cursed with a crude beam axle rear suspension and a McPherson strut front suspension whose geometry was designed around efficient packaging and relentless understeer rather than performance.  Because of this, the Sentra is at a significant disadvantage in the handling department when compared to its FWD rivals, mainly Hondas, the Scion TC and even the Infiniti G20.  Despite of all this, we at MotoIQ are always up to an engineering challenge and we set about to rework the SE-R's suspension to attempt to make it a little more competitive.

To read more about Project Spec-V click here!

The stock Sentra suspension is plagued by a bunch of soft squishy rubber suspension bushings.  Soft rubber is good for a smooth quiet ride but it hurts performance by making the alignment of the suspension inaccurate under load which makes it harder to keep the rubber on the ground. Soft rubber also makes the car slower to respond to steering inputs and dulls the driver’s feel of the car.

Sentra Spec-v bushings
Global performance Products came to our rescue by providing us with a set of hard 90 durometer polyurethane bushings for our front lower control arms.

Sentra Spec-V bushings

Global Performance Products also provided hard urethane rear trailing arm bushings.

B15 Sentra Spec-V caster bushing
A neat feature of the Global bushings is that they have an optional bushing with an offset hole that can be used to get additional positive caster in the suspension geometry.  This is good because positive caster causes the tire to lean into the turns when the wheel is turned helping traction.  Positive caster also helps stability.

B15 Sentra Spec-V trailing arm bushing
The stock rear trailing arm bushings are huge gushy doughnuts of rubber with cutouts that allows the rear suspension to move around over 1” under side load and braking.  That is not good.  The solid hard polyurethane cuts this down to very small fraction of an inch.

We are going to run a 235/40-17 NT01 tire on this car and the best wheel for this tire size is a 17x8” wheel.  We have also determined by measurement that an offset of 38-40mm is going to be needed to fit inside our wheelwells.  The trouble is that we were unable to find such a wheel in the lightweight forged construction that we require in the 4x114.3 bolt pattern that the Sentra uses.

However there are many quality wheels made in the 5 lug 5x114.3 bolt pattern that cars such as the EVO, STi, 350Z, RSX Type S and other cars use.  So the choice was simple, be stuck using ultra expensive custom wheels or to convert our car to 5 lug.

Sentra spec-v 5 lug conversion
Our front hubs were easy to modify.  We used ARP extended racing studs from a Spec Miata application, buying them from Summit Racing.  We simply drilled our hubs to the new bolt pattern using a turret vice on a drill press and pressed the new studs into the hubs with a hydraulic press.

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Comments
mikemiessler
mikemiesslerlink
Tuesday, April 20, 2010 8:06 PM
do you think these tricks would work on the B14 since the suspension is basically the same with floppy MacPhearson fronts and a torsion beam rear?
Mike Kojima
Mike Kojimalink
Tuesday, April 20, 2010 9:01 PM
Yes we did the same stuff on this car.
http://www.motoiq.com/MagazineArticles/tabid/59/articleType/ArticleView/articleId/1411/The-Dog-II.aspx
Bob Holmes
Bob Holmeslink
Wednesday, April 21, 2010 6:17 AM
Great job and some nice fab work. Did you use a computer model to determine your geometry changes? I still get a lot of satisfaction out of drawing them out on grid paper.
BenFenner
BenFennerlink
Wednesday, April 21, 2010 6:21 AM
I'm reading through the article and I like the simplicity of the 5-lug conversion on the front but the rear is more complicated. Was any thought given to beefing/welding up the rear hub so the same process could have been used?

Love those ARP wheel studs. I had endless problems with NISMO studs and fell in love with my ARP studs once I installed them. They are exceptional in every way.

Mike Kojima
Mike Kojimalink
Wednesday, April 21, 2010 4:37 PM
I probably should have figured out how to use the Maxima front hubs, I heard the RTR car used them.
sticky667
sticky667link
Wednesday, April 21, 2010 8:00 PM
from the Speed WC tech docs. looks like they only used the knuckle/hub and lower control arm. ball joint is larger but didn't matter since they relocated the pivot anyways. the arm matches up with the subframe mounts.
Joe
Joelink
Wednesday, May 05, 2010 9:00 PM
It was interesting to read the article, everything Mike was describing with the car I can relate to with my car.

I like the work done to convert the rear beam and the trick adjustable swaybay. My '96 Maxima has alot of load on the outside front wheel on hard cornering and bump steer issues from lowering. Adjustable bits are being made for the front suspension but I was stumped on how to reduce the roll center on the rear suspension, until now. Thank you for sharing with us Mike.

Also I agree that the NISMO wheel studs are not so good. I think a FWD car Running R compounds and track driving with them is looking for trouble. I stretched the threads and broke one stud after a two day track event at NJMP. I switched to ARP Mitsu EVO studs on all 4 corners and went back to NJMP with no wheel stud issues.
SE-Rviceenginesoon
SE-Rviceenginesoonlink
Saturday, May 15, 2010 11:33 AM
Mike - I have always wanted to mimic your tie rod end mod, and have discovered there are a lot of us sentra owners that want to as well. One owner has made adapter sleeves to change the thread pitch to standard, but I noticed you have found female M12x1.25 rod ends somewhere. So my ? is ... where, for the love of God, did you find those? I am only able to find M12x1.75's. If you were to point me in the right direction many of us would be super appreciative.
Mike Kojima
Mike Kojimalink
Sunday, May 16, 2010 11:32 AM
No they are 5/8"
Nismo Sentra S-Tune(99)
Nismo Sentra S-Tune(99)link
Thursday, July 01, 2010 3:19 AM
Hey, the relocation of the ball joints by welding a bung and using a heim joint...do you think something like that could be used on a street car? do you think it can handle the rigors of everyday driving and autox? Figure i'd ask the pro's before i attempt it, or should i be a guinea pig?
RedDragonV09
RedDragonV09link
Wednesday, January 05, 2011 10:14 AM
Hey Mike, Im in need of doing the bump steer fix and roll center fix to my b15 track car. Are you willing to release the measurments on all the hardware, where you got them, and a measurement of where to cut the control arm where you welded the bung for that spherical bearing? Id really appreciate the help!
Chris
Chrislink
Wednesday, April 25, 2012 4:46 PM
I know on one of the B15 boards, they have a sticky on how to convert the hubs to 5 lug without drilling the hubs. So if you want to do the 5 lug, you can do what they do
tkntez1
tkntez1link
Wednesday, January 23, 2013 8:19 PM
How important a consideration is the wall thickness of the panhard rod?
azmidlyf
azmidlyflink
Thursday, April 17, 2014 11:58 AM
How did you figure out the details on roll center? I always read of race teams altering suspension pick up points and figured it was to improve geometry. Has this car made the track yet?
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