Boxerworks.com

Hello again everyone!

I have a 1979 R100 RT that was in storage for over 10 years. I took it in to a BMW dealer today to have my new Shinko tires fitted and the mechanic said that after test riding it, he found that the rear shocks (which are the original shocks) are seized. He suggested and they have ordered a new set of Progressive Suspension 12 series Magnum shocks.

I'm not doubting the dealer, but was just wondering if anyone on this forum has any experience with the Progressive Magnum shock and if it is recommended?

Thank you!

Believe him when he says the originals need replacing - they all do.

What you replace them with depends on your wallet, how long you plan to keep the bike and the type of riding you do.

I went with a more affordable shock that is custom designed (spring weight) when you order them. They only have spring preload, which explains the good price, but they are worlds ahead of what was on my bike (and is on yours).

http://www.hagonshocksusa.com/

There are many other brands, of course.

"Seized" shocks? As in no movement? Does that square with your "seat of the pants" observations? To be sure, it's probably unreasonable to quibble about a recommendation to replace 34yr-old shocks---and he isn't recommending a set of Ohlins to go along with the Shinko tires. I have no experience with Progressive's shocks. Their forksprings that I did not care for seem to divide users among the "too stiff" (certainly they topped out my R90's front suspension pretty often) and "great handling improvement" camps. Certainly they're one of the lowest cost options, along with the Hagons. Is he going to re-use your original Boge springs, or are you buying complete 412 shocks?

I'm not sure how to tell if the shocks are seized, but when the mechanic moved the back of the bike up and down, there did not appear to be any movement. Plus, when I rode it about 2 weeks ago, it was an awful experience - it felt so hard and it was shaking. At first I thought that it was my tires, but it now turns out that the rear shocks are no longer providing any dampening.

The dealer went into the Parts Unlimited catalog and selected the Progressive 12 Series magnum shocks - part number PS-1203BG. He also ordered DS-310031 springs. I see now from a copy of the order that he only ordered one shocs and two springs. I wonder why he did that? It may have been an error, so I will call them when they open on Tuesday. If the dealer confirms that they made an error in the ordering, then that means the price for two shocks and the two springs will be $560. That's a fair chunk of change and if that is the case, I may tell them to cancel the order and I'll go with the Hagon shocks which I believe are priced at $245 for the set - I hope I'm reading their pricing correctly, I will call when they open tomorrow.

Any thoughts or comments would be appreciated!

Dang guys, this stuff is turning out to be expensive, but then again, I'm sure you know that better than I do....been spending way to much money to get my bike running...the little bits and pieces add up for sure.

Sigh...

Go with the Hagons, anything from a dealer will be twice as much...

Hagons are great value, though underdamped for two-up. Progressive fork Springs are good too though I have just changed mine for Sonics and like em better, about $100.

Not really related since the OP is in California in the Summer/Fall, but long ago I had a Mazda GLC (it was a great little car!) and one winter when the temps dropped below freezing, the rear suspension "froze up". The weather warmed up again and all was fine. Next time it got cold, same thing. New struts solved that problem.

justoneoftheguys wrote:Not really related since the OP is in California in the Summer/Fall, but long ago I had a Mazda GLC (it was a great little car!) and one winter when the temps dropped below freezing, the rear suspension "froze up". The weather warmed up again and all was fine. Next time it got cold, same thing. New struts solved that problem.

So the saying "Shock oil is like water" makes sense?

The factory rear shocks have 125mm or close to 5" of travel. None of the common replacements have anywhere near that. Most popular ones (Ikon and Hagon) are less than 3". I think Ohlins are the closest at just over 4" but at a cost of over $700.

That being said any new shock will be better than a seized one. I have had standard Hogons and they performed well for the price. Icons are nice as they are adjustable for dampening, which goes a long way to make up for the lack of travel and are rebuildable. Hagon 2810s are dampening adjustable and reasonably priced.

Interesting point about the shock travel comparison. I don't remember enough of my geometry and/or trigonometry to compute this myself, but there's at least a little bit involved in converting the shock's compressibility to a "suspension travel" figure at the axle. My Haynes manual agrees with Garnet that the /7 bikes had rear suspension travel of 4.92 inches/125mm, unless they had Nivomats, in which case it had a suspension travel of 3.37 inches/85mm. Ikon's chart does show the "Travel inches to bump stop" of their 7610-1298 shock absorber to be 2.95 inches/75mm. I'll leave it to more recently-practiced geometricians to determine what the "suspension travel" at the wheel axle would be with an Ikon shock that can compress only that much. Given the similarity in appearances of the progressive spring windings of the OE Boge shocks and present-day Ikons, it doesn't seem intuitive to me how the OE non-Nivomat Boge shocks would have had so much more travel before their springs and shock bodies would be fully compressed.