Hi guys, I have a 1990 K75s with an aftermarket rear shock that I understand to be the same height as a stock shock, 14". The bike is too tall for me. I also have a Corbin seat so I'd rather not go the lowerd seat route. EPN Performance Suspension in NJ, USA says they can build me a 13" YSS rear shock.
Before I go ahead I just thought I would see what the vast experience here has to say.
Thanks,
Chris

Most of the rebuilders can shorten a shock, so if you are unsure you can always use a knackered unit and have it rebuilt and shortened in one go that is even our old stock shocks hope this helps

I personaly would have a RAM SHOX, they make a short one at 13" http://www.realmengineering.com/page15.html

It is EPM Performance. I do work for them. We can build you a shock that is 13" and it will lower the bike just over 1". The YSS shock is rebuildable so it should be the last shock you have to buy. I have been running a YSS on my K1100lt for over 4 years now. I got it long before I started working there. We are able to service almost all the rebuildable after market shocks also. The model shock I have on my bike is a model 366. It has a threaded adjustable preload and adjustable rebound dampening. I believe they come with a 2 year warrantee. I am in the shop not a sales person. I am one of the guys doing the servicing and rebuilding. I am also an installer. If any of you saw our booth at the MOA national I was the short guy with the goatee. If anyone wants more info feel free to contact me.

My definition of motorcycling happiness is being able to get both heels on the ground at the same time.

When I was lowering my K1100LT about three months ago I came up with this:

Rear shock fully extended length between hole centres

k100v4/k1100lt/rs	385mm	15.16"
k75rt/s/k100rt/lt/rs	360mm	14.17"
k75/k100	345mm	13.58"

So I fitted an s/h K75 shock to my K1100LT.

After fitting the low shocks you may or may not need to adjust your front forks up or down in the triple clamps to match. Standard front sag is 1.75" on a K but mine was 3.5" due to old and soggy front springs. However this nicely matched the 40mm height reduction given by the K75 shock I fitted. Adjust your forks until the steering in a corner is neutral (check tyre pressures first etc.)

I was using the K75 shock as a cheap try-out and planning to buy a Realm unit 'cos I like their engineering. Trouble is I've fallen in love with my present low & soggy setup, its just what you need on the cart-tracks which pass for roads in Harlow.

I don't know how much you feel you need to reduce your K75 but with 40mm (~1.5") down on a K1100LT I can still hit a sleeping policeman at the legal limit and not ground out.

If you need more you can also get Corbin seats which are lowered.

Just to finish this thread I started, I did purchase a YSS 13" shock from EPM and it has been a treat for two seasons now, a beautiful piece of machinery! I have not bottomed out once, that may be a comment on my casual riding style but atleast my feet are flat on the ground now.
Thanks EPM

thanks for the report chris .....

worth remembering

good riding mate !

The beast lives and breathes. Some photos will follow… As soon as I can get out on a dry day to take them! I have been up and down the road literally no more than a couple of hundred yards.
I had a knackered saggy “std” shock on the rear. The damping was okay but it was really low.
I tried another “ditto” which made no difference.
I then acquired a saggy no damping K100 shock which set the ride height perfectly. However the bike is un-rideable because it bounces all over the place.
I also found this little table on this honourable website (which no one has contradicted).
https://www.k100-forum.com/t4608-rear-shock-height-problems
 

k100v4/k1100lt/rs	385mm	15.16"
k75rt/s/k100rt/lt/rs	360mm	14.17"
k75/k100	345mm	13.58"

 
So I have come to the conclusion that if the information is to be believed (no one has contradicted it), and measuring the length of them, I have 2x K100 shocks rather than 100LT shocks which accounted for the low/low ride height.
I think that if I get a 360 mm shock with a sidecar spring on it will get me to the right height I have now and it will not the doing a good impression of a kangaroo down the road.
I have spoken to Wasp who were friendly but couldn’t advise me on spring rates or lengths. I have spoken to Hagon who were extremely helpful with regard to the technicalities not with the lengths or spring rates.
Now, in my mind, I have decided what length to go for, I need to decide on a spring rate.
A few guys have posted on Facebook that they have had shocks from AVO which have been superb but as they are designed for cars, they don’t know anything about spring rates. They can supply them provided you give the details.
The beauty of them (I have used them on many many kit cars over the years and the quality is superb) is that not only are they fully rebuild the ball and extremely well made, they are under 150 quid each. The alternative is a RAM shock which would save something over the cost of a Hagon. I guess the knowledge which  Hagon have is what people pay for.
I am sorry to say that I know quite a few people who have fitted the basic non-rebuildable Hagon shocks and while they have been excellent when new, they simply don’t last. A friend of mine also fitted a Hagon shock (3 times!) on his Triumph Tiger and they had to keep replacing because it kept pissing oil out. He did say that their service was superb unfortunately he was less than impressed quality which is a shame.
The reports I have had have been extremely mixed. I did speak to a guy at the Stafford show who to be honest, should have been selling ice lollies.
If anybody’s got any ideas or experience preferably on LB/IN spring rates, it would be really gratefully received. You wouldn’t believe how long I’ve spent on Google trying to track something down in this respect but nothing exists that I could find.

Kind regards to all

That's an excellent post and relevant to me.

I have an 84 K100RT and it currently has a rear shock I took on a K100RS so it must be the 360mm unit.

So a swap to a base K75 or K100 spec would reduce seat height by 15mm? I hadn't realised they were different.

Reason I want this is that I acquired a new to me seat last week from Eire1400, instead of having my own recovered. Its in great condition but definitely taller than my existing one and I am challenged by the height. I guess I must pull the fork stanchions up too but since new seals are on the cards that's an easy fix.

Hi Guys, out of interest when I read this thread I went out to my 1990 K75 (naked low seat model with 17" rear wheel and rear disk brake) which I believe has the original shock on it and measured the length, eye to eye centres, as best as I could without removing it.

The magic number was 352mm which puts it right between two of the lengths in the table above. The shock does not have any damping adjustment, only 3 spring pre-load positions and the spring appears to be wound as a constant rate coil all of which makes me think it is the original. When I acquired the bike it had 77,000 km on it so I had the shock rebuilt (we have a company in Brisbane who will rebuild the "non-rebuildable" type shocks) and can't comment on whether the rebuild would have changed the length although I can't see how it would have.

Just thought I would confuse the issue!

Cheers

According to RealOEM the K75 to the end of 88 were #33531454833 and after that to the end of production the K100 and K75 were the same #33531450850. AFAIK there is no difference in length for K75 and K100 and the only difference is the K1100 is about 30mm longer.

I have been modding my bike to make it more comfortable for my size and style of riding for years. I ride pretty hard and get a bit sore in the back department.

Last year my rear shock absorber blew and I decided it was time to lower the beast and firm up the ride.

I spent about an hour in my local motorcycle dismantlers and walked away with a 12" adjustable shock from a Kwakka by memory.

I have done a few thousand kilometres with it fitted and after a couple of tweaks (set it as soft as possible actually) seem to have it just right. There is about 2" clearance between the underside of the rear guard and tyre and the two have not met yet!

I raised the front of the bike to the limit of the forks and I have fitted a comfort seat since the photo was taken. The ride is now perfect for me, it feels really agile yet comfortable.

One small problem in lowering the bike this much is that it is impossible to use the centre stand. So I removed it. 

I like that one and having had a Comfort seat on the LT agree its the best seat going.

I had struggled with the centre stand after an off last year and eventually it broke as I was trying to lever the bike up rather than lift it with the handle. Looks like I might just take it off too.

92KK 84WW Olaf wrote:I like that one and having had a Comfort seat on the LT agree its the best seat going.

I had struggled with the centre stand after an off last year and eventually it broke as I was trying to lever the bike up rather than lift it with the handle. Looks like I might just take it off too.

I had a King & Queen seat (as my mate has) and it was comfortably in the extreme. It would be great with a passenger (although I rarely ride with one) the problem is that because I’m almost 6’ and my mate is 6’2”, our knees hit the rubber of the fairing.
I have therefore take mine off will be going on eBay! It’s a shame. I actually have 2 of them one of them needs recovering.
I might get that done and pop that one on eBay also.

Hello!

For me the worst seat is good enough for me,
what I'm useing on my racing bicycle 100 miles tours, is good enough for my motorcycle. 
20 bucks, that's it and a day long trip is no problem :-)
Gel padded Bike shorts.

Cheers

touchwoodsden wrote:

92KK 84WW Olaf wrote:I like that one and having had a Comfort seat on the LT agree its the best seat going.

I had struggled with the centre stand after an off last year and eventually it broke as I was trying to lever the bike up rather than lift it with the handle. Looks like I might just take it off too.

I had a King & Queen seat (as my mate has) and it was comfortably in the extreme. It would be great with a passenger (although I rarely ride with one) the problem is that because I’m almost 6’ and my mate is 6’2”, our knees hit the rubber of the fairing.
I have therefore take mine off will be going on eBay! It’s a shame. I actually have 2 of them one of them needs recovering.
I might get that done and pop that one on eBay also.

Put on a K1100 fairing? its higher and further forward.

92KK 84WW Olaf wrote:

touchwoodsden wrote:
I have therefore take mine off will be going on eBay! It’s a shame. I actually have 2 of them one of them needs recovering.
I might get that done and pop that one on eBay also.

Put on a K1100 fairing? its higher and further forward.

Might be wortha try if I can find one

Touchwoodsden - getting back to the original theme (shock heights etc.) rather than comfort seats and padded underwear...
I got a RAM shock earlier in the year and have been very pleased with it's performance. 

It comes in a standard length - but as they are made to order, you could ask for a different size if needed. There is a fair amount of adjustment available, with the spring being preloaded according to expected bike loading so that the bike remains parallel with the ground when loaded.

I found the guys at Realm Engineering to be very helpful when I was ordering my shock - I recommend that you give them a call and I'm sure that they could advise you appropriately.

Copy of the set up instructions below...

Gaz80 wrote:The magic number was 352mm which puts it right between two of the lengths in the table above.

Did you measured with the bike on the centre stand and the rear wheel free of contact with the ground? If not, then you would have been measuring the shock length with static sag, which would be slightly shorter.

touchwoodsden wrote:

92KK 84WW Olaf wrote:

touchwoodsden wrote:
I have therefore take mine off will be going on eBay! It’s a shame. I actually have 2 of them one of them needs recovering.
I might get that done and pop that one on eBay also.

Put on a K1100 fairing? its higher and further forward.

Might be wortha try if I can find one

I've just thrown one in the skip! Sorry.

Motorbike Mike wrote:

touchwoodsden wrote:

92KK 84WW Olaf wrote:

Put on a K1100 fairing? its higher and further forward.

Might be wortha try if I can find one

I've just thrown one in the skip! Sorry.

That's life :-(

Sorry for resurrecting an old thread..
Tough
I came from supermoto world.. I know.. hooligans.. my bad. But now as 6 years ago went past 40   I try to pay my dues by giving a new life to an K100 and use as a daily ride an Aprilia Scarabeo vintage looking scooter.
Therefore my k100 build goes inevitable to scrambler world.
How 1100 handles those 25mm more rear shock spring?
Is this translated into near 3.5 cm rear height increase? Even if wheel travel is increased respecting sag rule that still means an increase of minimum 2 cm of rear height.
Is front height increased with those same 2cm?
Considering 18 inch rear option wheel that leads to more height.
If any ride those variants (100rs and 1100) please enlighten me.
I bought for my project an sourced Ohlins build for K100 (I think 16V) but it appears that the length is more close to an K1100. I'll retrofit however an K1100 paralever suspension but I don't know what to expect concerning rear ride height.
My problems get worse while I am struggling to fit KTM1290 Superduke USD fork witch is shorter than original k100rs fork. Off course I made some calculus and yes, taking sag into consideration front end will sit at the same height as with original fork.
But the main concern goes to rear end. How the bike will behave with increased ride height on the back?
I am hoping that BMW deliberately increased rear height using longer shock and larger wheel. If not, I'll have to alter shock mounting point on the frame witch I try to avoid. Off course I might choose a longer ktm fork but what if my legs are too short?

K75, early K100 RS up to 1989, K100RT and K100LT are 2v engines and are Monolever rear and use the shorter shock.

Post 89 K100RS and all K1100 are 16v engines and use Paralever rear and use the longer shock.

The configurations are very different and the Paralever rear uses the longer shock to preserve the geometry

You could put a 2v shock on a Paralever rear but I find it easy to ground a K1100 on corners. I am 70 kilos.