As described by John Cobb. I want to do some more experimentation with this on my road bike. Here’s how I understand it - get a shorter stem, Profile Jammer GT’s, drop seat about 1 to 1 1/2 inches below normal, slide seat right back as far as possible on rails. Then ride fast like a Euro pro(don’t I wish). Am I missing anything?
At Alcatraz last year I wasn’t down with cowhorns and clip-ons on a 78 degree bike, so I used my Colnago Dream “slammed out” a’la Cobbster. I did the Profile Jammer GTs but did not mess with my sacred saddle position. I just used my standard road position. I was in terrible shape but it handled and rode great on that hilly, pretty curvy course. It was a good move. That is not in strict compliance with the Cobb Big Slam standard, but is more the Demerly Gentle Slap. It worked fine. I hesitate to mess with my standard road bike seat position though.
cerveloguy. nobody is perfect, but i enjoyed riding the “slam” position last year. from my normal road position i studied mr cobb’s printed materials and ended up using a 1 cm shorter stem than i had - tho in truth i had been comtemplated doing that anyway - the slam bars, and really not moving my saddle much at all tho i did switch back to 170 from 175 mm cranks so i guess that counts for 5mm. if you do the set back from the bb mr cobb describes you would not , i don’t think, end up with the saddle all the way back al’a lemond-style nor would you lower the saddle an inch and a half (unless you were just being facetious). 
the thing that makes it work is the forward pelvic rotation. all in all, tho mr cobb has given it a catchy name and broke it down nicely, it is really just the proper way to sit on a bike, with a shorty bar added. if i may be so bold, i would say it is about the same as a nice tri position only rotated backwards around the bb a few degrees - or is that vice versa. a little higher in front, but also a little lower overall/in back. i like it fine.
I use the slam position on one bike and a semislam on another. My "road "and slam position are pretty close. I didn’t need a new stem or is my seat kicked back in the rails too much. I am 7.5cm benind bb on a plumb line at the nose of the saddle.
There are lots of variables out there on what the setup really is. My WTB seat has at least 1cm of unusable length of a nose on it, and each cm higher the bars go(ie spacer) effects the length of the cockpit you need.
The important thing is to get comfortable on the bike first, then make subtal changes. You have to watch out that you don’t run out of TT and get too much weight on the front end of the bike. My Merlin that is slammed could not be set into the “fast forward” position even though It has a 1cm longer tt than my semislam Javelin. The Javelin has a 78 degree seat tube as opposed to a 73 on the Merlin. In order to get the Merlin cockpit like the Javelin I would need a 15cm stem and about 70% of the weight would be on the front wheel. (I tried)
That is why a nice fitter is a good plan. Hope this helps. Aloha G
Actually, as I understood it, you drop the seat about an inch or more than normal and move the seat back at a 2:1 ratio. ie. drop the seat 2 cm and move it back 1 cm. I think I read this somewhere, but can’t remember where.
Tried it last year after no success on my 78 degree 650c wheel trike. The experiment was due to a herniation in my neck, c6-7 and the search for comfort and anything that I could ride without pain. DAy one consisted of a 100miler-8mile brick. Wow! I even ran better, so much for the got to ride 78 to save the legs scenerio and I’m a runner, 3:35 Ironman. Set up consisted of Cobbs position to a T, 72.5, down 1inch and slam bars made from an old set of mavic clip-ons. The frame is a LOOK 72.5deg. This year planning on doing Wildflower and Lake Placid in this position. One awesome aspect to the position, I’m no longer on a one dimensional bike! That said, don’t disagree with the 78 tri position but it has a place, semi flat course and a fast 40k in the extreme no heads up aggressive position it warrants. Hey Emp I’ll let you know how it work’s when I fly by you at Wildflower!!!
cerveloguy. there is no mention of a 2:1 saddle drop in the slam literature that mr cobb sends with the slam bars. maybe it is elsewhere. in the slam literature he does give saddle setback guidelines, and suggests dropping it a bit but an inch and a half is pretty marked. anyway as per a couple other guys my saddle was already where the set back guidelines called for. the most important thing, apart from the short bars, is the pelvic rotation.
I definately see a corelation (I can’t spell worth a darn, sorry) with a long femur bone and big slam: i.e. Big slam works best on riders with a longer femur bone. Any feedback?
tom. in my opinion “works BEST” is not really neccessarily the case. in my view it would work no more or less than the tri position based on femur length. the tri positon and the slam have, in my opinion, more in common than not. the main difference is where you are rotated around the clockface of the bb - forward and lower in front on the tri - rearward and higher in front/lower in back on the slam. i do not think your femur cares where you are on the clockface as its relative position to the center of the bb has really changed that much - it and you as a whole are simply rotating a tad. if you do not have good forward rotation at the pelvis in the slam, however, all bets are off. WITH forward rotation the hip angle is the same in both positions, as is the femur’s leverage.
Tom, I thing you may be right but what is the best way to decifer long femur info?
The “big slam” (the position existed a long time before cobb named it), works best only when the UCI mandates it for pro roadies:) Some people have noted that they didn’t move their seat after they got shorter stems and aero bars. In these cases, they are just riding a more compact position, not a more laid back “slam” position. Regardless, position is preference based, and steeper isn’t always practical for many people as noted. It’s just kinda of funny how everything has to have a buzzname (marketing name)
That said, having long femurs helps in just about all applications of applying force to pedals, with an exagerated effect on the over the top and down part of the stroke.
I take a standing inseam measurement using either a NECA Fitstick or their new-fangled measuring device- the spring loaded one. Then, I take a kneeling inseam using the Fit Stick and a Lufkin metric tape measure (most valuable tool in my store). Then I divide the smaller number (kneeling inseam) by the larger number (full or standing inseam) this gives me a number that usually looks like .456 or something similar. The larger the number, the longer the femur and, generally, the “vertical offset” is required between an imaginary vertical line bisecting the bottom bracket and another vertical line bisecting the center of the saddle. I just re-read that whole thing, I apologize, it is a little confusing. Can you make any sense out of it?
Ben, I agree but I do have an observation. Before Jon Cobb named and subsequently popularized the “Big Slam” we referred to it as the “Russian Position” since we observed a number of former Soviet/Eastern Bloc riders with their saddles far back and relatively low: Add a shorter stem and shorty (UCI legal) aero bars and you have “Big Slam”. I appreciate Jon Cobb’s work with it. His moniker for the position facilitates this type of discussion. If I run into a triathlete at a race almost anywhere and ask “Would you use a “Big Slam” set-up on this course?” He is likely to understand what I mean if he is familiar with current fit vernacular. I think there is some value in that, and I think Jon deserves recognition for that. Does anyone remember that Eddy Merckx bike Steve Bauer once used ('89,90?) that had 70 degree seat tube angle? That was like… “Thermonuclear Slam”.
When you say pelvic rotation I assume you really mean pelvic flexion, the motion of flattening or rounding the lumbar spine as opposed to extending the lumbar spine. To understand this difference pelvic/lumbar flexion could be demonstrated by laying on your back and placing a small cushion under your buttocks. Pelvic/lumbar extension would occur by placing the same cushion under the small of the back thus encouraging the lumbar lordosis. I assume the correct position that Cobb wants is a good degree of pelvic/lumbar flexion when riding in the slam position.
I can see the big slam position as possibly being problematic for riders who don’t have reasonable lumbar flexion or suffer from certain types of backache. I’ve tried riding in the slam position and it “feels” powerful, but I haven’t perfected it or spent enough time in this position to give a true verdict. I’ve never been totally comfortable in the 78 degree position, so I’m trying to find what works best for me. 76 degrees seems good, but I’d like to also give the slam a serious try.
I tried it a year ago. Rather than using JC’s bars, I installed the shortest stem I could find and stayed with my normal a-bars and cowhorns - don’t try a really short stem and road bars unless you have better reflexes than I do. My road saddle position was already well back, and I used that, but I also lowered the saddle to get the recommended knee bend. John and Dave were very good about getting back to me with answers to my questions.
I found the position comfortable, but wattage was practically the same as before after working on it for 6 - 8 weeks. I sometimes have tight hamstrings, so I evetually opted to go back to the more “open” forward position. The logic in that decision is not perfect, though, since John found that the Euro-guys were lowering their saddles to actually protect their hamstrings. At this down time of the year I’m contemplating trying it all over again.
Anyone interested should look at the three articles that John has on his Bicycle Sports website.
You wrote: “I’ve tried riding in the slam position and it “feels” powerful, but I haven’t perfected it or spent enough time in this position to give a true verdict.”
I did the same thing last year. I DEFINITELY FELT more powerful. But, I found out I was slower on a flat 10 mile tt. I’m sure I was faster going UP hills…just looking at the speed at the same place on the same hill on the same loop I ride all the time it was easy enough to see that fact. BUT, I lost too much aerodynamic efficiency on the flats to make it work for me. It could be that I was too high in the front, or not low enough in the rear, or whatever… I went back to 78 degrees and my speed returned.
Next year, I plan to use both positions, or something in between, depending upon the terrain of the race. One thing I definitely like about the rearward position is that it takes pressure off of my neck…MUCH easier to sit on a bike a long time and be able to see where I’m going!
This droping of the seat an inch is what confuses me. Once I get that dialed in on a bike I pretty much leave it as it is. It’s the other variable that I play around with - stem height, aerobar length, seat fore/aft on the rails.
My understanding of the Slam is riding in “normal” road position with shorter aero clip on bars mounted in a higher position
Finally found it. I knew I read this somewhere before. Read the section “Are forward position bikes always faster”. Here it is described lowering the seat by 1 to 1 1/2 inches.
Thanks for the link. I just read this.
This has been my thinking for some years now. I to have watched many a solo or two or three up break-away in a big pro bike race go on for an hour or two at very high speeds. This on regular road bikes riding in regular road position - but very low, powerful and as aero as you can get on a road bike. How is it that these guys can ride so fast. Do we just ditch this line of thinking and always go forward for fast TT’ing all the time. I recall reading once that Greg Lemond was more aero riding on his road bike on the drops than 99% of triathletes riding aero bars on tri-bikes!
It does make you wonder. I tried setting up my old steel road bike this way last year with the lowered seat, shorter stem, Profile Jammer GT’s. I only road this way a few times training to see what it was like. It “felt” powerful but as I never raced this way it’s hard to say. I think that I’ll set up my TCR for a sprint tri this way and see what happens. I honestly hope that after shelling out for a P2K this big slam thing isn’t that fast!!