Suspension geometry/design

SamDC5

Advanced Member
Messages
1,414
I thought it would be a good idea to create a thread in regards to the suspension geometry of the DC5/RSX/EP3 platform.

Any information you can share regarding bumpsteer, changes you've made to the geometry and how they've affected the car etc etc

Questions get asked a lot on Facebook etc so it'd be good for a hub of information to be posted on here.



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carl hammond

Advanced Member
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3,481
DC5 Integra Geometry and Bumpsteer Measurement Details in the below link:

My tried and tested suspension setups inc geo used at the time all in the link below:
 
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JustinEET

Active Member
Messages
83
DC5 Integra Geometry and Bumpsteer Measurement Details in the below link:

My tried and tested suspension setups inc geo used at the time all in the link below:
I was kinda disappointed that Honed never revisited their solutions to their findings. I was looking forward to it.
 

JustinEET

Active Member
Messages
83
I have two videos going over my research into Torque steer and Bump steer with this chassis.


So i've found that in order to satisfy proper geometry for minimal bump steer. That the coilovers should have an arm similar to the OEM strut. And that the Tie Rod end should connect from the top instead of inverted. This is how mine sits.
PXL_20201114_001324650.jpg

I was recently astonished that my research coincided with PCI's research(Which they have more money than me lol) so with access to a Bump steer gauge they also decided to go with the Tie rods connecting from the top. So I feel as though I did something right lol.
tieRod2.PNG
it appears they used washers while I just have one big spacer. Of course washers are more precise. But without bump steer gauge I can't really get precise.(I want to purchase one in the future).


Other than that due to the high steering rack placement another good modification to minimize bumpsteer is upgrading the steering rack slider to a thicker Delrin slider.
 

SamDC5

Advanced Member
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1,414
I was kinda disappointed that Honed never revisited their solutions to their findings. I was looking forward to it.
I think they're going to, their progress on the DC5 seems reallllly slow.

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24Lemons

Advanced Member
Messages
225
Does the EP3 suffer from bump steer? or is the DC5's issue mainly due to the high steering rack? Why does no one mention these issues with the FD2?

Internet generalisations;

DC5 bump steer.
EP3 vague electric steering.
FD2 rear suspension is a bit stiff.
 

Mark_teg

Moderator
Staff member
Messages
4,360
Does the EP3 suffer from bump steer? or is the DC5's issue mainly due to the high steering rack? Why does no one mention these issues with the FD2?

Internet generalisations;

DC5 bump steer.
EP3 vague electric steering.
FD2 rear suspension is a bit stiff.
The fd2 has a totally different designed suspension setup. Firstly, as you've mentioned, the steering rack is mounted far lower - this then results in the steering arm connecting to the hub rather than the suspension leg like on the dc5.
I'll see if I can find a picture of mine later
 

carl hammond

Advanced Member
Messages
3,481
Does the EP3 suffer from bump steer? or is the DC5's issue mainly due to the high steering rack? Why does no one mention these issues with the FD2?

Internet generalisations;

DC5 bump steer.
EP3 vague electric steering.
FD2 rear suspension is a bit stiff.
As Mark has said - The fd2 has a totally different designed suspension setup, however I keep seeing posts about issues with Bump Steer and I in 4 yrs of owning this one and driving loads in the past have never once experienced any bumpsteer on the road or track in a DC5....
 

24Lemons

Advanced Member
Messages
225
As Mark has said - The fd2 has a totally different designed suspension setup, however I keep seeing posts about issues with Bump Steer and I in 4 yrs of owning this one and driving loads in the past have never once experienced any bumpsteer on the road or track in a DC5....
Thanks for the info guys.

When I first got my car it had worn tyres and engine mounts, fair enough the guy was selling it, and it was all over the road with bump steer. New engine mounts and PS4 tyres completely eradicated this, even on bad surfaces. I am running stock suspension and hoping it will stay this way once I fit coilovers. I won't be lowering that much.

I think a lot of it is down to spending money on flash mods and not the boring maintenance bits, although I been there myself when I was younger.
 

carl hammond

Advanced Member
Messages
3,481
Thanks for the info guys.

When I first got my car it had worn tyres and engine mounts, fair enough the guy was selling it, and it was all over the road with bump steer. New engine mounts and PS4 tyres completely eradicated this, even on bad surfaces. I am running stock suspension and hoping it will stay this way once I fit coilovers. I won't be lowering that much.

I think a lot of it is down to spending money on flash mods and not the boring maintenance bits, although I been there myself when I was younger.
Completely agree, no bling here really, I just keep the car tip top and replace things where possible with OEM items and avoid cheap knock-off or copy parts as much as I physically can. I am a true believer that too many (far too many) just follow the crowd of people who have heard through 9 others that xyz works so do it (poxy rack raiser is a perfect example). These people don't care and just buy from companies making cheap copies, but in their eyes it's amazing so has to work and being cheap means it's a bargain... It was never like this back in the mid/late 90's when I started buying import cars, my first GTR (bought back in 2001) was a 1998 Silver R33 V-Spec and I had that and a Pulsar GTI-R, try getting copied parts back then. I assume the older owners of us are used to just buying proper parts and buying right first time maybe and annoyingly a lot of these cars (and many others like them) are plagued with poor maintenance, poor cheap copy parts and the result of which is, poor driving, poor handling, tatty examples that are plagued with issues
 
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SamDC5

Advanced Member
Messages
1,414
Does the EP3 suffer from bump steer? or is the DC5's issue mainly due to the high steering rack? Why does no one mention these issues with the FD2?

Internet generalisations;

DC5 bump steer.
EP3 vague electric steering.
FD2 rear suspension is a bit stiff.
The EP3 uses the same steering rack placement and the strut uses the same pick up point so the issues occur on both platforms.

I think the main issue is that Honda designed the front suspension to work in a narrow window.

If you look at some of the links posted my Justin on the analysis of the design of the front suspension, it was just never designed to work with a dramatically decreased ride height.

I can say that when I had my DC5 first setup, the car was set too low and I really hated how the car reacted on circuit.

I now run my car at a relatively high ride height for a track car and the improvement was noticed straight away.

The good thing about the YS dynamic pro sports is that the pick up point is nearly bang on for a fit and forget providing you run at a reasonable ride height for bump steer correction.

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moody_mage

Active Member
Messages
58
My mechanic recommended a rack raiser which I have. If I take it off do I need to redo alignment?
 

SamDC5

Advanced Member
Messages
1,414
My mechanic recommended a rack raiser which I have. If I take it off do I need to redo alignment?
The rack raiser can be used in certain situations but very likely it'll be causing issues more than fixing them. Unless it was fitted while measuring the geometry.

I'd say you'd need an alignment afterwards after removing.

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JustinEET

Active Member
Messages
83
PCI stated that stock the DC5 has the same amount of bumpsteer typical of any stock car.
But as Sam stated. Honda did create the DC5 with a very limited window. The closer to stock the better the geometry flows together.
So the cool part is figuring out how to maintain that while getting more performance features (lower center of gravity, camber angles, caster angles, etc)
So these rumors probably stemmed from early days of the DC5 with people lowering them too much without roll center adjustments and taking the high mounted steering rack into consideration.

Once you get that down. The DC5/EP3 are awesome cars.
Also another important thing to consider is how less of movement you want in the rear due to the motion ratio back there.
Which sits around .5
Also the DC5-R Front motion ratio is a tad lower than the DC5/EP3. Honda used a lighter and longer control arm upfront for the Integra Type R.
Some speculation behind it was for the Brembo's to maintain the same scrub radius while adding Brembo brakes.
Unfortunately we never got a Civic Type R here in the states until 2016 so I don't know if the EP3 Type R came with brembo's or not.
 
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carl hammond

Advanced Member
Messages
3,481
PCI stated that stock the DC5 has the same amount of bumpsteer typical of any stock car.
But as Sam stated. Honda did create the DC5 with a very limited window. The closer to stock the better the geometry flows together.
So the cool part is figuring out how to maintain that while getting more performance features (lower center of gravity, camber angles, caster angles, etc)
So these rumors probably stemmed from early days of the DC5 with people lowering them too much without roll center adjustments and taking the high mounted steering rack into consideration.

Once you get that down. The DC5/EP3 are awesome cars.
Also another important thing to consider is how less of movement you want in the rear due to the motion ratio back there.
Which sits around .5
Also the DC5-R Front motion ratio is a tad lower than the DC5/EP3. Honda used a lighter and longer control arm upfront for the Integra Type R.
Some speculation behind it was for the Brembo's to maintain the same scrub radius while adding Brembo brakes.
Unfortunately we never got a Civic Type R here in the states until 2016 so I don't know if the EP3 Type R came with brembo's or not.
The only EP3 with Brembos is the JDM EP3 which shares the K20A, ECU, LSD and gearing etc as the DC5, the EU versions had different gearing, K20A2 engine and no LSD etc (along with other differences).

Great info on her so far
 

Mark_teg

Moderator
Staff member
Messages
4,360
The only EP3 with Brembos is the JDM EP3 which shares the K20A, ECU, LSD and gearing etc as the DC5, the EU versions had different gearing, K20A2 engine and no LSD etc (along with other differences).

Great info on her so far
Carl, the JDM EP3 didn't come with Brembos either, it had 'Type-R' embossed calipers like the UK premier models.
 

carl hammond

Advanced Member
Messages
3,481
Carl, the JDM EP3 didn't come with Brembos either, it had 'Type-R' embossed calipers like the UK premier models.
Oh really? I’ve seen a few with them so assume they were added by people in Japan before exporting :)

The rest is correct though, learn something new everyday
 

Tuneboy

Advanced Member
Messages
102
Hi guys,
i will race my dc5 on rally-events next season so i try to dig deep in the suspension geo thingy.
Im aware of the Scrubradius. I think thats my first issue. Im running 8,5J with ET-35. I swapped Topmounts for Caster and i grinded the topmount holes more the the inner back. Im at -2,2° Camber at the moment, so with the increased camber i should be changing the SAI as well. Im unsure of how much Scrubradius i have left. I tried to measure it but its close to impossible with a cord and an McPherson Strut. I might just change to a rim with less offset and see how it drives.

Now to the Bumpsteer.
I also was in the believe that manufactors know what they are doing, and fitted Hardrace shperical inverted track rod ends. So I heard alot of negativety about this stuff and i am sure that ive done nothing good with that mod. BUT, i just dont understand why. If the tie rods are at an angle and move on the arc (=circle), the more they are on an angle, the more they move inwards (view from infront)! Hence changing toe, hence producing bumpsteer. If they are flat - or better, slightly leaned down, and the coil compresses, the movement ist mostly traveling up and down, and not inwards, without changing the toe that much.

I asked that in the facebook group but nobody could explain me exactly why it is. As i said. I am certain that its not good from what you heard from very clever people, but i cant get my head around it whys that.

So any help would be appreciated!
 

SamDC5

Advanced Member
Messages
1,414
Hi guys,
i will race my dc5 on rally-events next season so i try to dig deep in the suspension geo thingy.
Im aware of the Scrubradius. I think thats my first issue. Im running 8,5J with ET-35. I swapped Topmounts for Caster and i grinded the topmount holes more the the inner back. Im at -2,2° Camber at the moment, so with the increased camber i should be changing the SAI as well. Im unsure of how much Scrubradius i have left. I tried to measure it but its close to impossible with a cord and an McPherson Strut. I might just change to a rim with less offset and see how it drives.

Now to the Bumpsteer.
I also was in the believe that manufactors know what they are doing, and fitted Hardrace shperical inverted track rod ends. So I heard alot of negativety about this stuff and i am sure that ive done nothing good with that mod. BUT, i just dont understand why. If the tie rods are at an angle and move on the arc (=circle), the more they are on an angle, the more they move inwards (view from infront)! Hence changing toe, hence producing bumpsteer. If they are flat - or better, slightly leaned down, and the coil compresses, the movement ist mostly traveling up and down, and not inwards, without changing the toe that much.

I asked that in the facebook group but nobody could explain me exactly why it is. As i said. I am certain that its not good from what you heard from very clever people, but i cant get my head around it whys that.

So any help would be appreciated!
From my understanding, if the tie rod mounting is flat (along with the steering arms) then your IC lines dont meet up. As the suspension moves these lines change as the LCA moves in line with the tie rod. That's the relationship you're looking for.

Your LCA angle should not be flat just like your tie rod mounting position. (From my understanding).

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