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+--- Thread: Weird Suspension Design (/showthread.php?tid=5670)
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Weird Suspension Design - Paulb_imp - 01-07-2016
Today I collected my bike from Maxton Engineering (UK) where I've had their suspension fitted front and back. I'll do a report on that once I've got a few enthusiastic twisty miles under my belt but in the mean time I wonder if anyone can explain the unusual front suspension design that is fitted by Honda to the CB1100, it certainly caused a raised eyebrow at Maxton although they had occassionally seen this kind of thing before. Why would Honda fit different length springs to each of the fork legs and compensate by using odd length spacers? Are all CB1100's so equipped and if so, can anyone explain the engineering criteria behind such a design?
RE: Weird Suspension Design - LakeWylieJoe_imp - 01-07-2016
My '86 Nighthawk S has unequal spring lengths and spacers. The fork was designed that way so one fork leg could accommodate the TRAC anti-dive mechanism, which was only installed on one side.
I have no clue why this fork is designed this way, though. Maybe it's a way of getting two complimentary spring rates into play at the same time. Whatever it is, there was no doubt some reasoning behind it. They would have used common parts on both sides unless there was a reason not to.
I'd love to hear a Honda engineer explain...
I just looked at the US parts fiche for the '14 CB1100 standard and CB1100DLX, and both show a common spring and spacer part for both fork legs. Are you sure those parts came out of your fork?
RE: Weird Suspension Design - fritzwilliger_imp - 01-07-2016
(01-07-2016, 03:36 AM)Paulb_imp Wrote: Today I collected my bike from Maxton Engineering (UK) where I've had their suspension fitted front and back. I'll do a report on that once I've got a few enthusiastic twisty miles under my belt but in the mean time I wonder if anyone can explain the unusual front suspension design that is fitted by Honda to the CB1100, it certainly caused a raised eyebrow at Maxton although they had occassionally seen this kind of thing before. Why would Honda fit different length springs to each of the fork legs and compensate by using odd length spacers? Are all CB1100's so equipped and if so, can anyone explain the engineering criteria behind such a design?
Perhaps this was someone's "spring fling?"
My two cents... spoken with "forked" tongue...!
fritz
RE: Weird Suspension Design - Lord Popgun - 01-07-2016
Looking at the parts fiche it looks like there is only one spacer listed for all models/years. Used on both sides. So I don't know.
RE: Weird Suspension Design - flynrider - 01-07-2016
When the '14 DLX and EX came out, it was noticed that the service manual specified different amounts of fork oil for each leg (unlike the '13 models). The pic above definitely illustrates why they require different amounts, but I'm still mystified as to the reason for this asymetrical design.
RE: Weird Suspension Design - INTP_imp - 01-07-2016
This is just a guess, but maybe one side is set up for better compression dampening, and the other is set up for better rebound?
RE: Weird Suspension Design - Paulb_imp - 01-08-2016
(01-07-2016, 11:29 PM)INTP_imp Wrote: This is just a guess, but maybe one side is set up for better compression dampening, and the other is set up for better rebound?
I think you are in the right area. I suspect one spring only comes into play on rough, uneven road surfaces.
RE: Weird Suspension Design - Cormanus - 01-08-2016
Drat! I shall have to resort to the dreaded search function, but I'm sure this oddity has already been identified on the forum. I'm not sure anyone was able to explain the reason.
PS. Fritz, you really uncoiled with that post.
PPS. Try [url=http://cb1100forum.com/forum/showthread.php?tid=3773]here where our man TINK has posted an excellent how-to on replacing fork springs. His explanation for the longer spring in the left for of the DLX (and presumably the EX) is that it compensates for the extra weight.
RE: Weird Suspension Design - rboe - 01-08-2016
I think this topic came up in a book on Guzzi's. It's a rather trick way to have a sophisticated suspension with one leg responsible for one behavior, the other leg for a different one.
Apparently, being off center and asymmetrical does not bother the front one wit as the triple tree and axle join the assembly as one and it acts that way. The need to have the fork be mirror matches for each other is just a bias we have in our heads.
It came up in the Guzzi book where one grade of oil was used in one fork, a different grade in the other.
These motorcycle people can be quite clever at times.
Sometimes, too clever by half, but that's another topic.
RE: Weird Suspension Design - Django - 01-08-2016
My BMW K1100 had different dampers in each front fork leg, one for pull in one leg, one for push in the other leg. However, springs were the same in both legs.