Road course · Michigan, USA
Grattan Raceway
Grattan Raceway is a road course in Michigan. OpenStreetMap maps one layout here, 1.82 mi (2.92 km). Below: the map, every corner with a computed line, the elevation, and where to stay and eat.
- 1.81
- Miles
- 13
- Corners
- 52
- Ft of elevation
01Track map
Grattan track map
Full circuit
Name inferred by TRACK from the mapped loops, not an official layout name.
- Mapped length
- 1.82mi
- 2.92 km
- Direction
- Clockwise
- From OSM one-way tagging.
- Start/finish line
- Estimated
- Estimated by TRACK from the mapped geometry and not verified on site. TRACK asks you to confirm or move it before timing laps here, when you’re stopped.
- Corners
- 15
- Inferred from curvature, not official turn numbers
- Sectors
- 3
- Estimated, near each third of the lap
Source geometry: OpenStreetMap ↗. Something wrong? Fixing it in OpenStreetMap improves it for everyone.
02Overview
What Grattan is like to drive.
The full circuit layout at Grattan is 1.81 miles with 13 corners worth setting up for and about 52 ft of elevation change. A generic track-day car in our model brakes hard 9 times a lap and is at full throttle for about 37% of the distance; the longest straight runs roughly 1657 ft.
8 of the corners are slow (under 50 mph in the model), 0 are fast (over 75 mph). There are hairpins where exit speed matters more than entry. Some apexes sit on crests, where the car goes light. The corner notes below come from the mapped geometry, not from local knowledge; we’ll add a researched guide for Grattan later.
03Lap at a glance
Where the speed is, and where the hills are.
- Length
- 1.81mi
- Elevation range
- 52ft
- Steepest grade
- 6%
- Braking zones
- 9model
- Full throttle
- 37% model
- Longest straight
- 1657ft
The speed trace is a model, not a real lap: a generic track-day car (about 1.1 g of cornering grip, 1 g braking, 150 W/kg) driven on the computed line through an assumed 12 m wide track. Use it to see where the braking zones and flat-out sections are, not to predict your speeds. Elevation: USGS 3DEP 1/3 arc-second (NED 10 m) via OpenTopoData, sampled every 25 m along the mapped centerline.
04Corner by corner
The corners at Grattan.
TRACK’s own corner numbering (C1, C2…), found from the curvature of the mapped centerline. It isn’t the official turn numbering. Each diagram shows the computed line: the minimum-curvature path through an assumed 12 m wide track. It’s a geometric starting point. Your instructor’s line comes first.
- C1
Medium right-hander
↱ RightmediumhairpinTRACK numbering
A medium right-hand hairpin that turns about 140°, tightening to a radius of roughly 31 m (102 ft). The model car brakes for about 185 m (607 ft), from 132 to 51 mph. The computed line turns in from the left side, takes an apex close to the geometric apex, and lets the car run out to the left on exit.
- Turns
- 140° right
- Tightest radius
- 31 m
- Model speed
- 132 → 51 mph
- Braking (model)
- 185 m
- Grade
- +1.1%
- C2
Medium right-hander
↱ RightmediumcornerTRACK numbering
A medium right-hand corner that turns about 95°, tightening to a radius of roughly 26 m (85 ft). It drops through the corner (about 3% grade). The model car barely brakes here, carrying about 51 mph: a lift or a confident throttle balance. The computed line turns in from the left side, takes a late apex, about 10 m after the corner’s geometric apex, and lets the car run out to the left on exit.
- Turns
- 95° right
- Tightest radius
- 26 m
- Model speed
- ≈ 51 mph
- Braking (model)
- Lift / none
- Grade
- -2.8%
- C3
Slow left-hander
↰ LeftslowcornerTRACK numbering
A slow left-hand corner that turns about 122°, tightening to a radius of roughly 29 m (95 ft). The model car brakes for about 85 m (279 ft), from 81 to 47 mph. The computed line turns in from the right side, takes an apex close to the geometric apex, and lets the car run out to the right on exit.
- Turns
- 122° left
- Tightest radius
- 29 m
- Model speed
- 81 → 47 mph
- Braking (model)
- 85 m
- Grade
- -0.5%
- C4
Slow right-hander
↱ RightslowcornerTRACK numbering
A slow right-hand corner that turns about 80°, tightening to a radius of roughly 46 m (151 ft). The apex sits on a crest, so expect the car to go light. The model car barely brakes here, carrying about 47 mph: a lift or a confident throttle balance. The computed line turns in from the left side, takes an early apex, about 5 m before the geometric apex, and lets the car run out to the left on exit.
- Turns
- 80° right
- Tightest radius
- 46 m
- Model speed
- ≈ 47 mph
- Braking (model)
- Lift / none
- Grade
- -1.3% · crest
- C5
Medium left-hander
↰ LeftmediumchicaneTRACK numbering
A medium left-hand chicane that turns about 124°, tightening to a radius of roughly 30 m (98 ft). It drops through the corner (about 3% grade). The model car brakes for about 110 m (361 ft), from 101 to 59 mph. The computed line turns in from the right side, takes an early apex, about 100 m before the geometric apex, and lets the car run out to the right on exit.
- Turns
- 124° left
- Tightest radius
- 30 m
- Model speed
- 101 → 59 mph
- Braking (model)
- 110 m
- Grade
- -2.7%
- C6
Slow left-hander
↰ LeftslowchicaneTRACK numbering
A slow left-hand chicane that turns about 163°, tightening to a radius of roughly 30 m (98 ft). The model car brakes for about 40 m (131 ft), from 68 to 49 mph. The computed line turns in from the right side, takes an early apex, about 10 m before the geometric apex, and lets the car run out to the right on exit.
- Turns
- 163° left
- Tightest radius
- 30 m
- Model speed
- 68 → 49 mph
- Braking (model)
- 40 m
- Grade
- +1.1%
- C7
Slow left-hander
↰ LeftslowchicaneTRACK numbering
A slow left-hand chicane that turns about 194°, tightening to a radius of roughly 27 m (89 ft). It climbs through the corner (about 2% grade). The model car brakes for about 40 m (131 ft), from 68 to 49 mph. The computed line turns in from the right side, takes an early apex, about 65 m before the geometric apex, and lets the car run out to the right on exit.
- Turns
- 194° left
- Tightest radius
- 27 m
- Model speed
- 68 → 49 mph
- Braking (model)
- 40 m
- Grade
- +2.2%
- C8
Slow left-hander
↰ LeftslowchicaneTRACK numbering
A slow left-hand chicane that turns about 114°, tightening to a radius of roughly 24 m (79 ft). The model car barely brakes here, carrying about 42 mph: a lift or a confident throttle balance. The computed line turns in from the right side, takes an early apex, about 20 m before the geometric apex, and lets the car run out to the right on exit.
- Turns
- 114° left
- Tightest radius
- 24 m
- Model speed
- ≈ 42 mph
- Braking (model)
- Lift / none
- Grade
- +0.6%
- C9
Slow right-hander
↱ RightslowchicaneTRACK numbering
A slow right-hand chicane that turns about 79°, tightening to a radius of roughly 48 m (157 ft). The apex sits on a crest, so expect the car to go light. The model car barely brakes here, carrying about 42 mph: a lift or a confident throttle balance. The computed line turns in from the left side, takes an early apex, about 135 m before the geometric apex, and lets the car run out to the left on exit.
- Turns
- 79° right
- Tightest radius
- 48 m
- Model speed
- ≈ 42 mph
- Braking (model)
- Lift / none
- Grade
- -1.4% · crest
- C10
Slow right-hander
↱ RightslowhairpinTRACK numbering
A slow right-hand hairpin that turns about 151°, tightening to a radius of roughly 17 m (56 ft). The model car brakes for about 150 m (492 ft), from 103 to 39 mph. The computed line turns in from the left side, takes an early apex, about 5 m before the geometric apex, and lets the car run out to the left on exit.
- Turns
- 151° right
- Tightest radius
- 17 m
- Model speed
- 103 → 39 mph
- Braking (model)
- 150 m
- Grade
- -0.9%
- C11
Slow right-hander
↱ RightslowchicaneTRACK numbering
A slow right-hand chicane that turns about 67°, tightening to a radius of roughly 23 m (75 ft). The model car brakes for about 150 m (492 ft), from 103 to 39 mph. The computed line turns in from the left side, takes an early apex, about 65 m before the geometric apex, and lets the car run out to the left on exit.
- Turns
- 67° right
- Tightest radius
- 23 m
- Model speed
- 103 → 39 mph
- Braking (model)
- 150 m
- Grade
- -1.8%
- C12
Medium right-hander
↱ RightmediumessesTRACK numbering
A medium right-hand esses that turns about 56°, tightening to a radius of roughly 37 m (121 ft). It climbs through the corner (about 3% grade). The model car brakes for about 65 m (213 ft), from 89 to 62 mph. The computed line turns in from the left side, takes an apex close to the geometric apex, and lets the car run out to the left on exit.
- Turns
- 56° right
- Tightest radius
- 37 m
- Model speed
- 89 → 62 mph
- Braking (model)
- 65 m
- Grade
- +3.0%
- C13
Medium left-hander
↰ LeftmediumessesTRACK numbering
A medium left-hand esses that turns about 55°, tightening to a radius of roughly 23 m (75 ft). The model car brakes for about 65 m (213 ft), from 89 to 62 mph. The computed line turns in from the right side, takes an early apex, about 55 m before the geometric apex, and lets the car run out to the right on exit.
- Turns
- 55° left
- Tightest radius
- 23 m
- Model speed
- 89 → 62 mph
- Braking (model)
- 65 m
- Grade
- +1.9%
05Time it with TRACK
Drive Grattan. TRACK knows where you are.
No setup and no transponder. Start a session in the paddock and TRACK recognises Grattan and the layout from your GPS trace, then times every lap and sector with a live delta to your best.
- 1DetectTRACK matches your first few hundred metres against every mapped layout at Grattan, including shared pavement between configurations.
- 2Confirm the lineThe start/finish line here is estimated. When you’re stopped, TRACK shows it on the map: accept it or tap to move it. You’re never asked while driving.
- 3Laps, timed retroactivelyLaps you drove before confirming are timed from the recorded trace, so you don’t lose your first session.
- 4Go furtherSync a GoPro for video with telemetry and let TRACK Engineer point out where the time is. External 10–25 Hz GPS receivers for tighter sectors are awaiting hardware validation.
- Venue and layout detection is tested on simulated drives over real OpenStreetMap circuits, not yet in a real car. Compatible GPS receivers
06Plan your trip
Getting there, staying, eating.
Nearby places for Grattan haven’t been loaded yet.
07Track days
Find an open track day at Grattan.
TRACK doesn’t copy event listings. An on-page calendar will come with an organizer data partnership.
Before your first day here
08Nearby tracks
Closest mapped venues.
- Michigan International SpeedwayMichigan · 92 mi away
- Waterford Hills Road RacingMichigan · 104 mi away
- M1 ConcourseMichigan · 111 mi away
- Flat Rock SpeedwayMichigan · 127 mi away
Straight-line distance between venues. All 96 tracks
FAQ
Grattan, answered.
How long is Grattan?
The mapped centerline of Grattan Raceway is 1.82 mi (2.92 km) in OpenStreetMap. Published lengths are measured differently, so small differences are normal.
How much elevation change is there at Grattan?
About 52 ft (16 m) between the lowest and highest points of the full circuit layout, from USGS 3DEP elevation data sampled every 25 m. The steepest stretch is around 6%.
Which direction does Grattan run?
The main mapped layout runs clockwise, from one-way tagging in OpenStreetMap. Check the event’s driver briefing: some venues run reverse-direction days.
Can I time laps at Grattan with my phone?
Yes, with the TRACK iPhone app (beta). It recognises Grattan and the layout you’re driving from GPS, then times laps and sectors. A phone’s GPS is good for lap times; an external 10–25 Hz receiver tightens sector splits.
Where is the start/finish line at Grattan?
TRACK estimates the line from the mapped geometry (usually beside the pit lane, or on the longest straight). It isn’t verified on site, so the app asks you to confirm or move it before timing your first session here.
How do I find track days at Grattan?
Clubs and organizers list HPDE, track days and club races on MotorsportReg. The venue’s own calendar lists its events too. TRACK doesn’t list events itself.
Where can I stay near Grattan?
This page lists hotels, campgrounds, restaurants, fuel and parts stores near Grattan from OpenStreetMap, with straight-line distances. Book early for big event weekends.
Track geometry and nearby places: © OpenStreetMap contributors, available under the Open Database License 1.0 (via the TRACK Atlas, snapshot 2026-10-17). Elevation: USGS 3DEP (public domain). Lengths are mapped centerlines, not official figures. The computed line and speed trace are a model. No start/finish line has been verified on site.
TRACK is not affiliated with or endorsed by Grattan Raceway, MotorsportReg or any business listed here. The venue name identifies the location only and belongs to its owner. TRACK shows no lap records or official results for this venue. Driving advice is general: your instructor, the event’s rules and the venue’s rules come first.